United States Climate – Sep 2026September 2026 Update
The United States recorded its warmest September in 77 years of records, capping an unprecedented quarter that also marked the warmest late-summer stretch ever observed nationwide.
Key States: California, Texas, Florida, New York, and Alaska
Summary
The United States recorded its warmest September in 77 years of records, capping an unprecedented quarter that also marked the warmest late-summer stretch ever observed nationwide. Pervasive atmospheric high pressure trapped unseasonable heat across the central interior, pushing nocturnal low temperatures to record levels for tens of millions of residents. A strong El Niño in the tropical Pacific is intensifying and forecast to peak at Very Strong late in the year, with unseasonably elevated warmth projected to persist across much of the country through autumn.
This month in numbers
The average temperature across the United States in September 2026 reached 20.79°C, standing 2.8°C above the 1961–1990 baseline and ranking 1st out of 77 years on record. Average daytime maximum temperatures reached 27.42°C, registering 2.4°C above normal and ranking as the 3rd highest on record. Total precipitation averaged 68.33 mm, slightly above average by 1.1 mm and ranking 26th. Looking at the three-month period from July to September 2026, the nationwide average temperature of 23.31°C (+2.2°C anomaly) and average maximum temperature of 30.26°C (+2.0°C anomaly) both set all-time record highs.
What changed
The relentless late-summer warmth pushed the July to September period to the top of historical records, surpassing all previous three-month spans. On a global scale, land temperatures ranked 2nd warmest for the month (+1.9°C anomaly) and 3rd warmest for the July to September season (+1.8°C anomaly). Nationally, the US sits 0.64°C warmer than the broader North American regional average (+1.83°C anomaly). Crucially, 8 of the top 10 highest 1-month anomalies across all tracked global regions were US states, headed by Oklahoma at +5.87°C and Arkansas at +5.33°C.
What’s driving change?
Persistent and pronounced anchored severe late-season heat over the Central Plains and Midwest. Because surfaces, inland regions absorbed exceptional energy during daytime hours and struggled to cool overnight. The current climate background is further influenced by a strong El Niño in the Pacific, tracked at ENSO, which historically redistributes global atmospheric heat and favours milder temperatures across northern states during autumn. A positive Arctic Oscillation also contributed to keeping Arctic air locked far to the north.
Looking ahead
Seasonal forecasts from NOAA indicate a high probability of above-average temperatures continuing across the central and eastern United States over the coming months, accompanied by typical El Niño moisture patterns spreading across the southern states.
Precipitation, Sunshine, Frost and Snow are converted to standard deviations from their own average so they can share an axis with Temperature anomalies.
Metric
Insight
Temperature
10-Yr AverageActual Year
Climate History
86 of 86 events
1910Other
The 1910 'Big Burn'
Still the largest fire season on record in the Northern Rockies - hundreds of fires burned ~3 million acres (roughly the size of Connecticut), most of it in just two days in late August. 87 deaths, 78 of them firefighters.
The largest volcanic eruption anywhere in the world in the 20th century - 13 km3 of magma, about thirty times the 1980 Mount St. Helens eruption - at Novarupta in Alaska on 6-8 June 1912. Ash reached 100,000 ft and cooled the Northern Hemisphere by roughly 0.3°C over 1912-13. Unlike a tropical eruption such as Pinatubo, a high-latitude eruption's haze stays in its own hemisphere, so it did little to the Southern Hemisphere.
Severe drought and dust storms across the US Great Plains. Unusual sea-surface temperatures in the tropical Pacific and Atlantic caused the drought; ploughing up native grassland for crops turned it into a disaster, leaving bare soil for the wind to take.
The single worst dust storm of the Dust Bowl era, centered on the Oklahoma/Kansas panhandle border - ~300,000 tons of topsoil displaced in one day, directly spurring the federal Soil Conservation Act.
Category 3 landfall near Newport, >120mph winds, 12-15ft storm surge at high tide put parts of downtown Providence under 14ft of water. ~600 regional deaths - Rhode Island was hardest-hit.
After the Second World War, coal and oil use grew rapidly across Europe, North America and the Soviet Union. Global sulphur dioxide emissions rose from about 30 to about 130 million tonnes a year by 1980, and the sulphate haze they formed masked part of the greenhouse warming underneath - the effect known as 'global dimming'.
The drought of the 1950s was among the most widespread, severe and sustained ever recorded in the United States. In several states it beat the Dust Bowl. It began in the south-west around 1950, spread to Kansas and Oklahoma by 1953, and by 1954 covered a ten-state area from the Midwest through the Plains and into the Deep South. For much of the Southern Plains it is still the drought of record - the benchmark every later drought is measured against.
Between 24 August and 6 September 1953 the north-eastern United States recorded 1,097 readings above 90°F, 546 above 95°F and 129 above 100°F. New York City spent twelve consecutive days in the 90s. At least 59 people died directly of the heat in that fortnight, and 576 across the year - most of the country from the Rockies to the Atlantic was described at the time as suffering its worst heat and drought since the Dust Bowl.
One of the strongest La Niñas since instrument-based ENSO records begin in 1950, and part of a run of cool Pacific years through the mid-1950s. La Niña cools global temperatures slightly for a year or two while it lasts, and shifts rainfall patterns worldwide.
Charles David Keeling begins continuous measurements of atmospheric CO₂ at Mauna Loa Observatory in Hawaii, starting at about 315 ppm. The record has risen every year since and is now the longest unbroken direct measurement of CO₂ anywhere - the 'Keeling Curve'.
From autumn 1961 to summer 1966 the Northeast went through what is still its drought of record. By March 1966 it was the longest and most severe on the books; New York City's reservoirs fell to about a quarter of capacity. The climatologist W.C. Palmer judged 1965 so rare an event that the region should expect it only about once in two centuries. In this site's own data 1965 is the driest year on record in eight states, and fifteen states have their driest year somewhere inside 1962-66.
About 14 inches of rain fell near Castle Rock and Deckers on 14 June 1965, and two days later the South Platte tore through Denver. Peak discharge reached 40,300 cubic feet per second - 1.8 times the previous highest in records going back to 1889. Property losses came to $543m at the time, over $4.4bn in today's money, and it remains the most expensive flood in Colorado's history. 1965 is Colorado's 2nd-wettest year in this site's 1950-2025 record.
Camille came ashore near Bay St. Louis, Mississippi on the night of 17 August 1969 as one of only four Category 5 hurricanes ever to make landfall in the continental United States, with re-analysed peak winds near 175 mph. It drove a 24.6 ft storm surge into Pass Christian - the largest measured in the US until Katrina beat it at the very same town 36 years later. Two days later its remnants stalled over Virginia and killed 113 people in flash floods. Around 256 deaths in total.
This is a US law, and its clearest effects were felt here first. The 1970 Clean Air Act set strict national standards for sulphur dioxide and particulates, and American skies got measurably cleaner over the following decades. There is a climate sting in that success: sulphate aerosols reflect sunlight, so removing them removed a cooling effect that had been partly masking greenhouse warming. Cleaning the air was unambiguously right for human health - it also revealed how much warming had already been bought and paid for.
One of the strongest El Niños on record. It contributed to failed grain harvests in the Soviet Union and elsewhere in 1972, and to a sharp rise in world food prices - an early sign of how far ENSO's reach extends.
Agnes came ashore in Florida in June 1972 as a weak hurricane, then stalled over the Mid-Atlantic and became the most destructive hurricane in US history to that point: 117 deaths and $3.1bn of damage across 12 states. Pennsylvania took the worst of it, with Susquehanna discharges higher than anything since European settlement.
The Mississippi reached flood stage on 10 March 1973 and did not fall below it until 26 May. Vicksburg recorded 88 consecutive days of floodflow and St. Louis 77 - both records. The river crested at St. Louis on 28 April at 12.2 ft over flood stage, its highest level in more than 150 years. Over 12 million acres were inundated, 30,000 homes damaged and 33 people died.
A short but intense drought running from northern Minnesota to southern California. It was the most severe on record in northern California at the time - reservoirs failed to refill and the state introduced widespread rationing - and it brought record low water levels to the Upper Midwest, the Mississippi among them. Because it lasted only two years it is not usually counted among the great multi-year droughts, but its peak was as sharp as any.
The 1976-77 Pacific Decadal Oscillation flip is felt most directly in the western United States, where the PDO's phase helps set how wet or dry winters run and how much snow the mountains hold. The warm phase that began then persisted for about two decades, and its onset coincided with the severe 1976-77 drought in California and the Upper Midwest.
Global sulphur dioxide emissions peak at about 130 million tonnes a year, then begin a long decline as Europe, North America and Japan clean up their air. As the aerosol mask thins, the rate of global warming picks up through the 1980s.
A high-pressure ridge sat over the central and southern United States from June to September 1980, pushing temperatures above 90°F almost daily and capping thunderstorm formation so that heat and drought reinforced each other. At least 1,700 people died - some counts put it above 1,860 - making it one of the deadliest weather disasters in US history, with around $20bn of agricultural losses at the time.
A sulphur-rich eruption in Mexico whose aerosol cloud stayed in the stratosphere for more than two years, cooling the Northern Hemisphere by about 0.2°C.
For the United States this was a strong event with a strongly uneven footprint. The southern tier took the storms - a severe winter storm season along the California coast and flooding on the Gulf - while the northern states ran mild and dry. On NOAA's RONI index, which strips out background ocean warming before ranking events, this is the strongest El Niño since 1950, ahead of both 1997-98 and 2015-16.
British Antarctic Survey scientists Joe Farman, Brian Gardiner and Jon Shanklin publish their Halley and Faraday measurements on 16 May 1985, showing October ozone over Antarctica had fallen to about two-thirds of earlier decades. The cause is traced to chlorofluorocarbons, and the finding triggers the fastest international environmental response on record.
Signed in 1987 to phase out ozone-depleting chlorofluorocarbons, the Montreal Protocol turned out to be one of the most consequential climate treaties ever agreed. CFCs are potent greenhouse gases in their own right, and NOAA estimates the Protocol prevented up to 2°C of warming by 2100 - around 1°C from the emissions avoided, and up to 1°C more by sparing forests and other carbon sinks from increased ultraviolet radiation.
The 350 ppm threshold has a specifically American moment attached to it: in the same year, 1988, James Hansen told a US Senate committee that warming was 'unequivocal' and already detectable. That testimony is usually taken as the point at which climate change entered mainstream American politics. The measurement itself was made, as all of them are, at Mauna Loa in Hawaii.
One of the strongest La Niñas on record, arriving directly after the 1986-87 El Niño. For the United States it matters as a cause rather than a curiosity: it is a major driver of the 1988 Midwest drought and the Yellowstone fires of that summer. La Niña tends to push the jet stream north, leaving the central and southern US hot and dry.
The 6th-worst natural disaster in US history by cost at the time - extreme Midwest summer drought/heatwave, associated with extensive wildfires in and around Yellowstone National Park (Northern Rockies).
Hugo came ashore just north of Charleston at Sullivan's Island around midnight on 22 September 1989 as a Category 4, with sustained winds estimated at 135-140 mph. It drove a 20 ft storm surge into McClellanville - the highest storm tide ever recorded on the US East Coast - and killed 86 people, 35 of them in South Carolina. It remained a damaging windstorm as far inland as Charlotte.
Daytime warming catches up with the night-led pattern
Across 1961-90, 81% of the world's land saw nights warming faster than days. Across 1991-2020 the pattern reversed: 70% saw days warming faster, as the industrial haze that had been dimming daytime sunshine was cleaned up. The study compares two fixed thirty-year windows; measured as a turning point, this site's own global series turns around 1982.
Pinatubo's aerosol veil is visible in the United States' own record. 1993, two years after the June 1991 eruption, is the 4th-coldest year in the US series and the coldest since 1979 - and no year since has been colder, which makes it the last genuinely cold year the country has had. A single large eruption can hold temperatures down for two or three years; it cannot reverse the trend, and the US record since 1993 shows exactly that.
Andrew struck south Florida on 24 August 1992 as a Category 5, coming ashore over Elliott Key and then Homestead. It destroyed more than 63,500 houses and damaged over 124,000, killed 65 people and caused $27.3bn of damage - about $65bn in today's money, and the most expensive natural disaster in US history until Katrina thirteen years later.
The Mississippi at St. Louis crested at 49.58 ft, its highest stage ever recorded, and the Upper Mississippi saw its greatest flood on record. $36.3bn in losses and 48 deaths. It was a whole summer of rain rather than one storm: 1993 is still the wettest year on record in Iowa, Illinois and Nebraska.
Atlantic Multidecadal Oscillation flips to a warm phase
The Atlantic Multidecadal Oscillation flipped to a warm phase in 1995, and for the United States that matters most through hurricanes: warm AMO phases are associated with more active Atlantic hurricane seasons, and the period since 1995 has included Katrina, Sandy, Florence and Harvey. The AMO is a natural cycle running over roughly 60-70 years, so it is not a warming signal in itself - but it changes the baseline that warming is added to.
A warm subtropical jet arrived over deep fresh snow on 6 February 1996 and melted it. Everywhere west of the Cascades took at least seven inches of rain, the mountains over twenty. The Willamette crested at 28.6 ft in Portland, where volunteers built a plywood wall on top of the seawall to keep the river out of the city. Eight people died and damage reached $700-800m. 1996 remains the wettest year on record in Washington, Oregon and Idaho alike.
For the United States this is often treated as the textbook strong El Niño, and the textbook pattern is a split one: a stormy, wet winter across the southern tier, from California to Florida, while the northern half of the country ran exceptionally mild, with monthly means 6-16°F above normal across parts of the northern Plains.
1-3in of ice accretion from prolonged freezing rain; 900,000 Mainers lost power, all 16 counties declared federal disaster areas, ~$320m damage. Called a 100-year event.
A strong La Niña that ran for three winters after the record 1997-98 El Niño, peaking at an ONI of -1.53. Its US signature is drought across the southern tier: every one of the six states where this site's data shows a real ENSO rainfall signal came in below average that first winter, New Mexico by 63% and Louisiana by 52%. It overlaps the 1999-2002 Eastern drought.
Pacific Decadal Oscillation flips back to a cool phase
The Pacific Decadal Oscillation returned to a cool phase around 1998-99. Cool phases tend to favour drier conditions across the south-western United States, and the period that followed contains the Southwest megadrought that began in 2000 - a natural cycle setting the stage, with warming then deepening the effect.
A multi-year drought across the Northeast and Mid-Atlantic, peaking in 2001. New York and New England saw conditions not seen since the 1960s; New Jersey declared a statewide water emergency in March 2002 after ten of twelve months came in below normal; Virginia's 1999-2002 drought is its worst of the modern era. In this site's own data 2001 is the driest year on record in Maine and Vermont and the 2nd, 3rd or 4th driest in seven more states.
Two waves of extreme heat and humidity in July 1999 killed well over 150 people in the Midwest and Mid-Atlantic. Over the Independence Day weekend, heat indices near 110°F in eastern Pennsylvania were linked to 74 deaths, most in and around Philadelphia. At the end of the month Chicago reached over 100°F with an all-time record dew point of 82°F at Midway, and NOAA's storm record lists 99 heat deaths in the Chicago area.
Lake Mead and Lake Powell (the two largest US reservoirs) have hit repeated record lows since 2021. Udall & Overpeck (2017): roughly a third to a half of the 21st-century Colorado River flow decline is attributable to higher temperatures alone, separate from precipitation.
2002 was the sharpest single dry year of the early Southwest megadrought. It is the driest year on record in Colorado in this site's 1950-2025 series, and among the driest in Nevada, Arizona, Utah and Wyoming. It produced the Hayman Fire in Colorado and the Rodeo-Chediski fire in Arizona, each the largest in its state's recorded history at the time.
Katrina crossed south Florida as a Category 1, intensified to Category 5 over an unusually warm Gulf, and made its main landfall near Grand Isle, Louisiana on 29 August 2005 as a Category 3. Levee failures flooded about 80% of New Orleans; Pass Christian, Mississippi recorded a 27.8 ft storm surge, the highest ever documented in the United States. 520 direct deaths and ~$108bn damage, the costliest US hurricane at the time.
Between 7 and 16 October 2005 the remnants of Tropical Storm Tammy and Subtropical Depression Twenty-Two merged with cold fronts over interior New England and dropped 6 to 15 inches of rain. It was the wettest month ever recorded in Concord, New Hampshire (14.57 in, in records back to 1868) and in Providence, Rhode Island (15.38 in). In Alstead, New Hampshire an embankment failure on the Cold River sent a 20-30 ft wave through the village, destroying 40 homes and killing four people.
2006: a national heat record that lasted six years
2006 was the warmest year ever recorded for the contiguous United States, edging past the 1998 El Niño record. A severe heat wave ran from mid-July into late August, killing at least 225 people; on 17 July all but three states reached 90°F or more, and California's central valley hit 110-115°F. In this site's data 2006 now ranks only 10th warmest nationally.
A severe drought across the south-east from 2006 into 2008. It is the driest year on record in North Carolina and Tennessee, and the lowest year for relative humidity on record in five of the seven states it covers. Lake Lanier, Atlanta's water supply for more than three million people, reached record lows by December 2007. Florida's began earliest - Key West took 1.05 inches of rain in the 175 days to 14 May 2006, its driest stretch ever recorded.
On the night of 4 May 2007 a tornado 1.7 miles wide destroyed about 90% of Greensburg, Kansas. It was the first tornado rated EF5 on the new Enhanced Fujita scale, with winds of about 205 mph, and the strongest since the 1999 Bridge Creek-Moore tornado. It killed 11 people in the town of about 1,500, and 13 across the outbreak.
A moderate-to-strong El Niño that peaked around the turn of 2009-10. It helped make 2010 one of the warmest years on record at the time, and was followed straight away by the strong La Niña of 2010-12.
Globally, heatwave days have roughly doubled each decade since 2010 - from an average of 5.3 a year in the 2000s to 11.5 in the 2010s and 18.9 so far in the 2020s, weighted by land area across 169 countries. El Niño has not become more extreme. The whole temperature distribution has shifted upwards, so the same natural El Niño and La Niña cycle now pushes far more days over fixed extreme-heat thresholds.
A strong double-winter La Niña peaking at an ONI of -1.57, and the direct driver of the worst single-year drought in Texas's history. Texas's winter rainfall ran 37% below its 1961-90 average, New Mexico's 46% below and Louisiana's 43% below. Texas's driest 12 months on record, October 2010 to September 2011, sits inside this event.
Start of the sustained rise in US heatwave frequency
Averaged across the 50 states, Heatwave Days (WSDI) sat between 4.2 and 6.4 days a year in every decade from the 1950s to the 2000s, then jumped to 10.5 in the 2010s and 12.9 so far in the 2020s. 48 of the 50 states now record more heatwave days than they did in 1961-90, though how much more varies enormously from state to state.
The Northeast recorded its warmest January-August period on record in 2010, 3.4°F above the long-term average, with Maine, New Hampshire, Vermont, Rhode Island, Connecticut and New Jersey each posting their warmest year-to-date. Nationally it was the 4th-warmest US summer. In July alone close to 9,000 daily temperature records were broken or tied.
2011 is the wettest year on record in six eastern states, for two quite different reasons. In the Ohio Valley, record April rain fell on an already saturated basin carrying one of the largest snowmelt surges on record, driving the Ohio and lower Mississippi to levels not seen since 1937 and 1927. In the Northeast, Tropical Storm Irene in August and the remnants of Lee two weeks later finished a year that had already had a very wet spring.
An EF5 tornado about a mile wide tracked 22 miles through Joplin on the evening of 22 May 2011, killing 161 people and injuring more than a thousand. It is the deadliest single tornado in the United States since official records began in 1950.
At its July 2012 peak the drought covered about 70% of the United States and nearly 40% of its agricultural land was in severe drought or worse - the largest moderate-to-extreme drought area since the 1950s. It affected around 62% of farms and 88% of the corn crop, and cut barge traffic on the Mississippi. In this site's own data it shows as heat and dryness arriving together across the Plains, Midwest and Southwest.
The most intense hurricane on record to make landfall north of Cape Hatteras and the largest Atlantic hurricane by diameter (tropical-storm-force winds spanning 1,150 miles). ~$70bn damage (2012 dollars), 254 deaths across 8 countries. Sea surface temperatures off the Northeast coast were 3.0°C above average when it strengthened.
2012: the warmest year on record for the contiguous US
2012 was the warmest year ever recorded for the contiguous United States, 3.2°F above the 20th-century average and a full 1.0°F above the previous record, 1998. March 2012 was the warmest March on record, breaking more than 15,000 daily records, and 19 states had their warmest year.
Atmospheric CO₂ passes 400 ppm at Mauna Loa on 9 May 2013 - a level the planet had not seen for 3-5 million years, since the Pliocene, when sea levels were many metres higher.
8 of the 10 warmest years in the US national record have occurred since 2013, the start of the Post-Hiatus Acceleration era - and every one of the 50 states has at least 6 of its own 10 warmest years since 2000. The clustering is near-universal across the country, even where individual states' warmest years fall in different summers.
At 10:37 on 22 March 2014, a rain-soaked hillside above the North Fork Stillaguamish River near Oso, Washington, collapsed. Some 18 million tons of sand, mud and debris crossed the valley at around 40 mph, burying the Steelhead Haven community and State Route 530. It killed 43 people - the deadliest landslide in US history.
By the raw ONI index this was the strongest El Niño ever measured, which makes what happened in the United States instructive: Southern California's winter was close to ordinary and the drought was not broken, even though Northern California did get solid rain. A strong index does not guarantee a strong local outcome. This site's own per-state analysis says the same thing - of the 50 states, only Florida, Texas, New Mexico and Hawaii show a winter-rainfall relationship with ENSO strong enough to explain a fifth or more of the year-to-year variation, and Florida is the only one where it is really pronounced.
Globally, the eleven warmest years on record have all happened since 2015. The United States' own record is a looser fit: eight of its eleven warmest fall in that span, with 2012, 2006 and 1998 outside it, while 2018, 2019 and 2022 sit inside the span but outside the US top eleven. Drought-stricken 2012 is still the second warmest year in the US record, and the warmest is 2024.
Across the south-east, nights have been warming faster than days for the whole of the record, and the gap has closed fastest since about 2003. Comparing 2015-2025 with 1950-2014, Louisiana, South Carolina and Florida show the three largest narrowings of any US state, and the eight biggest are all south-eastern: nights up roughly 1.4°C, days about 0.8°C. It is the clearest regional expression in this site's US data of the single most diagnostic signature of greenhouse warming.
Comparing 2015-2025 with 1950-2014, relative humidity has fallen across every western state - Utah by 3.9 percentage points, Colorado 3.6, New Mexico 3.5, California 3.4. The eight largest falls in the country are all western. Then a clean break. Across the humid south-east the change is a tenth of a point or less, and in two states relative humidity actually rose. The country is splitting into a drying West and an unchanged East.
In 2015, 454 of the West's 559 monitored snow sites - 81% - recorded their lowest snowpack ever measured, and at 111 of them the 1 April snow water equivalent was zero for the first time on record. California and Oregon finished about 90% below normal. What makes it important is the cause: precipitation was not unusually low in much of the region. It was exceptional warmth, so what fell came as rain and what lay melted early.
Harvey stalled over south-east Texas in August 2017 and dropped 60.58 inches of rain near Nederland - the highest total from any tropical cyclone in United States history. Large parts of Houston flooded, and damages reached around $125bn. Five separate attribution studies have since examined the rainfall, and all found a climate-change fingerprint in it.
Nine eastern states - Delaware, Maryland, Massachusetts, New Jersey, North Carolina, Pennsylvania, Tennessee, Virginia and West Virginia - all recorded their wettest year on record in 2018, and more than two dozen cities did too, Washington DC and Pittsburgh among them. Nationally it was the 3rd-wettest year in 124 years of records. No single storm explains it: it was a run of heavy rain events on already-saturated ground.
May 2019 brought 200-400% of normal rainfall to southern Kansas and northern Oklahoma, and the water came down the Arkansas River. Fort Smith broke its 1945 record crest of 38.1 ft twice inside a week, finally reaching 40.79 ft on 1 June. A levee near Dardanelle lost a 40-foot section to the current. Five people died and damage across the basin reached about $3bn.
In September 2019 a stubborn ridge parked over the Southeast and produced record heat with almost no rain. The area in drought grew from 25% to 80% in a single month. Mississippi, Alabama, Georgia, Florida, Kentucky and West Virginia all recorded their driest September in records back to 1895, and it was the joint 2nd-warmest September in the contiguous US. This is a textbook flash drought. Heat and sunshine drove it, not simply an absence of rain.
2019 was the wettest year on record for the Midwest as a whole in records back to 1895, and for five individual states in this site's own series. South Dakota's was the most extreme anywhere: 66% above its 1961-90 average, beating its previous record by almost a quarter. Rapid snowmelt onto saturated ground brought record spring flooding, and planting was delayed across the region on a scale not seen before.
Global fossil CO₂ emissions fell about 5.8% in 2020, from 37.0 to 34.8 billion tonnes, yet atmospheric CO₂ still rose 2.5 ppm - the dip barely registers in the atmospheric record. Emissions were back to pre-pandemic levels by 2022.
New international shipping rules cut the sulphur allowed in ship fuel from 3.5% to 0.5% almost overnight, removing about 8 million tonnes of sulphur dioxide a year. With less sulphate haze over the oceans, it may have added around 0.1°C of warming by 2023-24.
Three consecutive La Niña winters - a 'triple dip', which has happened only a handful of times since 1950 - peaking at an ONI of -1.11. The rarity is the duration rather than the strength, and the US rainfall response was correspondingly patchy: New Mexico ran 37% below its 1961-90 average that first winter, but South Carolina ran 17% above.
On 10 August 2020 a derecho ran 770 miles in 14 hours, from south-east South Dakota to Ohio. Gusts reached a measured 126 mph at Atkins, Iowa, with an estimated 140 mph in Cedar Rapids. Around 14 million acres of Iowa cropland were damaged - roughly half of everything planted in the state that year - and the $11.2bn bill makes it the costliest thunderstorm event on record anywhere in the United States.
The December 2021 western Kentucky tornado outbreak
On the night of 10-11 December 2021 a violent EF4 tornado crossed western Kentucky on a 165.7-mile track - one of the longest tornado paths in US history - destroying much of downtown Mayfield, including its courthouse and a candle factory where people were working the night shift. With a second long-track tornado the same night, it killed 58 people in Kentucky; the outbreak was the deadliest December tornado outbreak on record.
Over the Christmas weekend of 23-27 December 2022 a 'bomb cyclone' brought a flash freeze, gusts over 70 mph and lake-effect snow to western New York. Six to six and a half feet of snow fell on Buffalo's southern suburbs, and the city was paralysed for days. At least 44 people died in the region, many of them found outside in the snow or in stranded cars.
A strong El Niño arriving on top of long-term greenhouse warming, with the cut in shipping sulphur from the 2020 fuel rule adding a little more. Together they produced the record global temperatures of 2023 and 2024.
Helene made landfall in the Florida panhandle on 26 September 2024 as a Category 4, then carried catastrophic rain hundreds of miles inland. Parts of western North Carolina took more than 30 inches. In Asheville the French Broad River passed the 1916 flood record by over a foot and a half. More than 250 people died nationally, 107 of them in North Carolina - the deadliest hurricane to strike the US mainland since Katrina.
The Palisades and Eaton fires broke out on 7 January 2025 and burned into Los Angeles itself. Together they killed 31 people and destroyed more than 16,000 structures - 6,837 in Pacific Palisades and 9,414 in Altadena and Pasadena. A rapid attribution study found climate change made the fire-prone conditions about 35% more likely, and responsible for roughly a quarter of the available fuel.
Overnight into 4 July 2025, storms fed by moisture from the remnants of Tropical Storm Barry stalled over the Texas Hill Country and dropped 2-3 inches of rain an hour onto the headwaters of the Guadalupe River. The river rose more than 20 feet in a few hours through Kerr County, sweeping through riverside homes and summer camps. More than 130 people died across central Texas, over 100 of them in Kerr County, among them children at Camp Mystic.
Source: NOAA Climate at a Glance — US states & climate regions (tavg, pcp), plus GPCC (Snow, water-equivalent). Anomalies are vs the 1961–1990 baseline. See methodology.
United States has a temperate climate (Köppen Cfa: Humid subtropical), with distinct warm summers and cool-to-cold winters. July is typically the warmest month, averaging 24.2°C, while January is the coldest at 0.4°C. Annual precipitation averages around 795mm (about 86mm of it as snow), spread fairly evenly across the year.
Warmest month
Jul 24°C
Coldest month
Jan 0°C
Annual rainfall
709mm
Wettest month
May 84mm
Annual snowfall
86mmwater-equiv.
Snowiest month
Jan 18mm
RainSnow (water-equivalent)
Monthly climate normals (2016–2025) - bar colour and height show average temperature, the shaded area shows average monthly rain, with snow (water-equivalent) shown separately.
Data: NOAA National Centers for Environmental Information (temperature/precipitation; frost: World Bank CCKP; snow: GPCC (DWD)).
How spring and autumn have shifted in United States. Spring is defined as the date monthly temperatures first rise above the long-term annual mean (11.0°C, from 1950–1979); autumn is the date they fall back below it. Temperature swings 24.5°C peak-to-peak across the year - a classic four-seasons rhythm.
Shifting summer
9 days Longer
Warm Season
1950–1979 Baseline: 19 Apr → 22 Oct · 186 days
2016–2025 Now: 15 Apr → 27 Oct · 195 days
JanJFebFMarMAprAMayMJunJJulJAugASepSOctONovNDecD
Spr 4 days EarlierAut 5 days Later
baseline yr·recent yr·ring = global temp anomaly
1950–19792016–20251950–1979 annual mean
Baseline vs recent monthly temperature climatology. Biggest warming: Mar (+2.1°C).
Data: NOAA National Centers for Environmental Information (temperature/precipitation; frost: World Bank CCKP; snow: GPCC (DWD)).
Live GDACS alerts in the United States - Red (Major), Orange (Severe) or Green (Moderate) - and the long-term record of weather and climate disasters.
Live Alerts
Loading…
Alerts, Last 12 Months
Major
0
0.8 a year since 2021
Severe
1
2.3 a year since 2021
Moderate
119
Weather Disasters in 2024 - Latest Complete Year
Disasters
29
27 a year, 2015-2024
Deaths
1,464
493 a year, 2015-2024
Weather Disasters, 2015-2024
Most Frequent
Storms & Cyclones
174 of 268 disasters
Deadliest
Storms & Cyclones
2,541 of 4,926 deaths
Disasters: EM-DAT, CRED / UCLouvain, via Our World in Data - 10+ deaths, 100+ people affected, or a declared emergency or call for international help. Alerts: GDACS.
The natural climate patterns that measurably shape seasonal temperature or rainfall in the United States, from this site’s own data since 1950 - long-term trends removed, and ENSO’s share taken out before scoring the others, so each is credited only for what it adds.
El Niño / La Niña (ENSO)moderate link
The tropical Pacific’s warm and cool swings - the biggest natural driver of year-to-year climate.
Now: El Niño (strong) · RONI +1.7°C(Jul-Sep 2026)
Forecast - 100% very strong at peak, Sep-Nov, then neutral by Apr-Jun 2027 (NOAA). La Niña from Oct 2027 in SNU’s AI model.
A moderate or strong link for 22% of the places in this group.
Every figure on this page is sourced from official, openly published climate datasets. Anomalies are calculated against the 1961–1990 baseline (temperature) and 1991–2020 (rainfall, sunshine, frost) - see the Methodology & Sources page for the complete dataset list and update calendar.
The United States is warming in line with the rest of the world. The page above shows the latest monthly temperature anomaly versus the 1961-1990 baseline, the long-term annual trend, and the region's rank in the historical record. The headline panel also shows the long-term trend rate per decade and the warmest and coolest years on file.
What is the climate like in the United States?
The United States has a temperate climate (Köppen Cfa: Humid subtropical), with distinct warm summers and cool-to-cold winters. July is typically the warmest month, averaging 24.2°C, while January is the coldest at 0.4°C. Annual precipitation averages around 795mm (about 86mm of it as snow), spread fairly evenly across the year.
Which climate drivers affect the weather in the United States?
Measured from seasonal temperature and rainfall in the United States since 1950, with the long-term warming trend removed (and ENSO's own share removed before scoring the other drivers), the climate drivers with a clear effect here are: El Niño / La Niña (ENSO) - a moderate or strong link for 22% of the places in this group; the North Atlantic Oscillation (NAO) - a moderate or strong link for 67% of the places in this group; the Pacific-North American pattern (PNA) - a moderate or strong link for 61% of the places in this group; the Arctic Oscillation (AO) - a moderate or strong link for 45% of the places in this group. Their current state is shown in the Climate Drivers section of this page.
What extreme weather affects the United States?
In 2024, the latest complete year, the international disaster database EM-DAT recorded 29 weather and climate disasters in the United States, against an average of 27 a year in 2015-2024, with 1,464 deaths. Over those ten years the most frequent type was storms & cyclones (174 of 268) and the deadliest storms & cyclones. GDACS, the UN and European Commission's disaster alert system, issued 0 Major (Red) and 1 Severe (Orange) alerts for the United States in the last 12 months. Live alerts are on this page and on the Extreme Weather tracker.
Where does the climate data for the United States come from?
Climate data for the United States comes from NOAA Climate at a Glance (temperature and precipitation), Our World in Data, sourcing Copernicus ERA5 and HadCRUT5 (national temperature anomaly) and the Global Carbon Project via Our World in Data (CO₂ emissions), refreshed every month, when the upstream temperature and rainfall data are refreshed.
What is the climate baseline used on this page?
Anomalies on this page are calculated against the 1961-1990 climatological baseline, which is the standard reference period used by the Met Office, NOAA, IPCC and most national climate services. Some panels also show the source-native 1901-2000 (NOAA) or 1991-2020 (WMO) baselines for verification. See Methodology & Sources for the full reference.
Which areas does the United States climate data cover?
The United States climate profile covers California, Texas, Florida, New York and surrounding areas. The world's second-largest emitter and energy transition leader
How often is the United States climate update refreshed?
The United States climate update is refreshed monthly, typically a few days after the previous month closes and the upstream provider (Met Office HadUK-Grid, NOAA Climate at a Glance, Copernicus ERA5 or the Global Carbon Project) publishes its update. See the Climate Rankings for cross-region comparisons.
What counts as a Heatwave Day on the United States climate page?
Heatwave Days use the Warm Spell Duration Index (WSDI) - the WMO/ETCCDI-standard heatwave measure: days that are part of a run of 6 or more consecutive days above the local 90th-percentile temperature for that calendar day. The 90th-percentile threshold varies by time of year (a hot day in January is judged differently to one in July) but is fixed to the 1961-1990 baseline for every year shown - it does not shift as the climate warms, which is why Heatwave Days trend upward over time.
Does the United States climate page include frost and snow data?
Yes. Frost Days (days with a minimum temperature below 0°C, World Bank CCKP) and snow water-equivalent (GPCC) are shown alongside temperature and precipitation, each measured against the 1961-1990 baseline where a like-for-like historical comparison is available.
What major climate events has the United States experienced?
Major climate events in the United States include The 1910 'Big Burn'; The South Platte flood of 1965; 1988 Midwest drought / Yellowstone fires; The July 1999 heat wave; The Greensburg tornado (2007); 2012: the warmest year on record for the contiguous US; 2018: the wettest year on record across the East; Hurricane Helene (2024). The Climate History panel on this page lists 86 sourced events and pattern shifts relevant to the United States, the earliest from 1910 - 52 about the United States itself and the rest global context such as volcanic eruptions and El Niño events. Each entry carries its own sources and can be searched, filtered to local events or by category, and sorted by date; scrolling the list moves a cursor across the chart above so you can see where each event falls in the record.
Where does the Climate History list for the United States come from, and how is it checked?
It is a hand-reviewed register, not an automatic feed. Every entry is sourced, and each one records how it was verified - against this site's own data series, against a peer-reviewed paper, or against the public record of the event. 14 of the 86 entries here are written specifically about the United States, usually quoting its own ranking or measured figures. The rest give global or national context shared with wider pages. Where a figure is narrower than it first appears, or a famous claim does not hold locally, the entry says so.
Are nights warming faster than days in the United States?
The Long-Term Trends chart has a Day/Night toggle showing Day Highs and Night Lows anchored around the average trend, so they always bracket it rather than both drifting to one side. Across most of the world, nights warmed faster than days from the 1960s to the late 1980s (air pollution dimming daytime sun), and days have generally been catching back up since, as skies cleared. Toggle Day/Night on the chart above to see which pattern the United States follows.
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