US Northeast Climate – Sep 2026September 2026 Update
The US Northeast experienced noticeably warm conditions during September 2026 as late-summer heat extended into autumn, leaving the region well above historical baselines…
Top States: New York, Pennsylvania, Massachusetts, New Jersey, and Maryland
Summary
The US Northeast experienced noticeably warm conditions during September 2026 as late-summer heat extended into autumn, leaving the region well above historical baselines. Elevated temperatures were widespread across the Mid-Atlantic portion of the group, where several states registered monthly anomalies exceeding 1.7°C, though northern areas saw milder departures. As seasonal patterns shift, long-range forecasts indicate that warmer-than-average conditions are likely to persist across the region in the coming months.
This month in numbers
For September 2026, the US Northeast recorded a 1-month average temperature anomaly of +1.36°C relative to the 1961-1990 baseline. The broader regional trend remains consistently elevated, reflected in a 3-month anomaly of +1.24°C and a 12-month rolling anomaly of +0.86°C. On the global stage, warmth across the country was a defining feature, as 8 of the 10 warmest regions in the 1-month cross-region rankings were US states.
Hottest & coolest US states
Anomalies were highest in the southern portion of the region, led by Delaware US Delaware with a 1-month departure of +2.07°C and Maryland US Maryland at +2.01°C. Pennsylvania US Pennsylvania also ran significantly above average with an anomaly of +1.88°C, followed closely by New Jersey US New Jersey at +1.73°C. By contrast, northern states experienced more moderate warmth, with New Hampshire US New Hampshire recording the coolest anomaly in the group at +0.81°C.
What's driving change?
across the eastern United States allowed summer heat to linger well into autumn, illustrating the fundamental principle that . In addition, seasonal shifts are increasingly compressing traditional winter cold spells and delaying autumn cooling across northern latitudes, keeping regional baselines elevated above historical norms.
Looking ahead
According to official long-range outlooks from the NOAA Climate Prediction Center, the US Northeast faces an increased probability of above-average temperatures continuing over the next 1-3 months.
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
46 of 46 events
1912Volcanic
Novarupta (Katmai) eruption
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.
Up to 9in of rain on already-saturated soil; 85 deaths, 1,285 bridges destroyed - Vermont's worst natural disaster until Tropical Storm Irene (2011), which VT officials repeatedly described as the worst since 1927.
A Category 3 landfall that killed around 600 people, and still the defining storm of the southern New England coast. It hit Connecticut, Massachusetts, New York and Rhode Island.
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'.
One of the most widespread hot summers in the US record: a top-five heatwave year in 23 states. In the Northeast that included Connecticut, Delaware, Massachusetts, Maryland, New Jersey, New York, Pennsylvania and Rhode Island.
Tree-ring reconstructions suggest this may be the worst mid-Atlantic drought in several hundred years; the Delaware River was reduced to 'a trickle', with saltwater intrusion and water rationing.
The drought of record for the Northeast, when New York City's reservoirs fell to about a quarter of capacity. It reached every state in the region - Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island and Vermont - though how hard it hit varied a good deal from one state to the next.
The 1970 Clean Air Act cut sulphur dioxide and particulate pollution across the country, and removing those sunlight-reflecting aerosols also removed a cooling effect that had been partly masking greenhouse warming. Across the Northeast, 2006-2025 averaged +1.28°C warmer than the two decades before the Act, 1951-1970.
Three severe winters in a row. January 1977 was probably the coldest month the eastern United States had seen in two centuries - Atlanta's coldest month ever measured - and the winter of 1978-79 was the coldest on record for the contiguous United States. Missouri had its coldest winter on record; Illinois had its coldest January-February, 14°F below normal, with seventeen major winter storms.
The Pacific Decadal Oscillation is a North Pacific pattern, and its influence on this side of the country is weak and indirect - mostly through how it nudges the winter jet stream downstream. Its 1976-77 flip marks a genuine shift in Pacific-basin climate, but for eastern states the Atlantic Multidecadal Oscillation is the ocean cycle that matters more.
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 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.
El Niño has no reliable rainfall signal in the Northeast, but it tends to bring mild winters. 1982-83 ran +2.4°C against the 1961-90 average, with rainfall -13%. On NOAA's RONI index, which strips out background ocean warming, this is the strongest El Niño since 1950.
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.
Mild winters made 1990 the 7th-warmest year then recorded in the contiguous United States, and the 4th-warmest in the Northeast. January-February 1990 set the national record for those months, which stood until 1998, and 1991 was nearly as warm across much of the East.
Pinatubo's cooling is only faintly visible in the Northeast's own record. 1993, two years after the June 1991 eruption, ranks 23rd-coldest of the 76 years there, though 1997 has since been colder. A single large eruption can hold temperatures down for two or three years; it cannot reverse the trend.
Atlantic Multidecadal Oscillation flips to a warm phase
The Atlantic Multidecadal Oscillation flipped to a warm phase in 1995, and for the Northeast its reach is through the Atlantic hurricane season: the warm phase since includes Irene in 2011 and Sandy in 2012. It is a natural cycle of roughly 60-70 years, so it shifts the baseline rather than driving the long-term trend.
El Niño has no reliable rainfall signal in the Northeast, but it tends to bring mild winters. 1997-98 ran +3.6°C against the 1961-90 average, with rainfall +28%. It is often treated as the textbook strong El Niño.
An ice storm that left 900,000 people without power in Maine alone, and became one of the costliest disasters in Canadian history across the border. It hit Maine, New Hampshire, New York and Vermont.
Pacific Decadal Oscillation flips back to a cool phase
The Pacific Decadal Oscillation returned to a cool phase around 1998-99. Its direct effects are western - drier conditions across the south-west, changes in North Pacific fisheries - and its influence on this side of the country is weak and indirect. The Atlantic Multidecadal Oscillation, which flipped warm in 1995, is the ocean cycle with more bearing on eastern weather.
A multi-year drought whose 2001 peak is still the driest year on record in Maine and Vermont. It also reached Massachusetts, Maryland, New Hampshire, New Jersey, New York and Pennsylvania.
Over the Independence Day weekend of 1999, heat indices near 110°F gripped the Mid-Atlantic. NOAA's storm record links 74 deaths in eastern Pennsylvania and 4 in Delaware to the heat.
The highest heatwave-day count on record in Delaware and Massachusetts. It is also a top-five heatwave year in Connecticut, Maryland, New Hampshire and New Jersey.
One of the wettest years on record across the Mid-Atlantic, ranking 2nd in Maryland, Virginia and West Virginia. In the Northeast it is a top-five wet year in Delaware, Maryland and Pennsylvania.
2006: a national heat record that lasted six years
The warmest year ever recorded for the contiguous United States at the time - since pushed down to 10th. In the Northeast it is still a top-five warm year in Maine and Vermont.
Start of the sustained rise in US heatwave frequency
Across the eleven states of the Northeast, Heatwave Days (WSDI) rose from a 1961-90 average of 2.8 days a year to 5.5 in 2016-25 - a rise of 97%, with 10 of the 11 recording more heatwave days than in 1961-90. The spread inside the region is very wide: New Hampshire 3.7x against Connecticut 0.8x.
The Northeast's warmest January-August on record, with warm-night records falling at more than twice the rate of warm-day records that July. It covered Connecticut, Maine, Massachusetts, New Hampshire, New York, Pennsylvania, Rhode Island and Vermont.
The largest Atlantic hurricane on record by diameter, with around $70bn of damage. It hit Connecticut, Delaware, Maryland, New Jersey, New York, Pennsylvania and Rhode Island.
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.
Across the eleven states of the Northeast, an average of 5.5 of each state's ten warmest years have come since 2013, ranging from 5 in Connecticut to 7 in Delaware. Every state in the region has at least 7 of its ten warmest since 2000.
In early January 2014 the polar vortex slipped south and Arctic air spread from the Rockies to the Atlantic, affecting more than 200 million people. Chicago fell to -16°F on 6 January, and the cold returned in waves into March. It made 2014 one of the coldest years of recent decades across the Midwest and the South.
El Niño has no reliable rainfall signal in the Northeast, but it tends to bring mild winters. 2015-16 ran +4.4°C against the 1961-90 average, with rainfall +20%. By the raw ONI index it was the strongest El Niño ever measured - a reminder that a strong index does not guarantee a strong local outcome.
Globally, the eleven warmest years on record have all happened since 2015. The Northeast follows it only partly: five of its own eleven warmest fall in that span, with 2012, 2011, 2010, 2006, 1998 and 1990 outside it. Its warmest year is 2024.
Ellicott City's two '1000-year' flash floods, 2016 & 2018
Two catastrophic flash floods in the same small watershed 22 months apart: July 2016 (6in in 90min, a 1-in-1000-yr event) and May 2018 (8.4-10.4in, likely also 1-in-1000-yr). NOAA/USGS jointly studied both.
Wilmington recorded 61.37in of rain, breaking the 1945 record (61.05in) - part of a multi-city record-wet year across the Northeast (DC, Baltimore, Pittsburgh also set records that year).
The year nine eastern states all set their wettest year on record. Five of them are in the Northeast: Delaware, Maryland, Massachusetts, New Jersey and Pennsylvania.
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.
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.
Warm Spell Duration Index (WSDI) - days in a 6+ day run above the local 90th-percentile temperature for that time of year.
Heatwave days per year2010 (Record)10-yr avg
Data: World Bank Climate Change Knowledge Portal (ERA5-derived), aggregated by 4BYO across member states. Refreshed roughly 1-2x/year, ~7-8 months behind present.
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.
How spring and autumn have shifted in US Northeast. Spring is defined as the date monthly temperatures first rise above the long-term annual mean (7.5°C, from 1950–1979); autumn is the date they fall back below it. Temperature swings 26.4°C peak-to-peak across the year - a classic four-seasons rhythm.
Shifting summer
10 Days Longer
Warm Season
1950–1979 Baseline: 20 Apr → 25 Oct · 188 days
2016–2025 Now: 15 Apr → 31 Oct · 199 days
−5d+6d
JanJFebFMarMAprAMayMJunJJulJAugASepSOctONovNDecD
Spr 5 Days EarlierAut 6 Days Later
baseline avgrecent avgClickTap for decades
1950–19792016–20251950–1979 annual mean
Baseline vs recent monthly temperature climatology. Biggest warming: Feb (+3.0°C).
NOAA Climate at a Glance — regional tavg. Baseline: first 30 yrs on record. Recent: last 10 yrs on record.
The natural climate patterns that measurably shape seasonal temperature or rainfall in the US Northeast, 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.
Weaker Links
A small signal in one season - easily outweighed by other weather, and possibly partly chance.
AOweak link45% of places in this group show a moderate or strong linkPolar Vortex / AO
NAOweak link36% of places in this group show a moderate or strong linkNAO Tracker
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 US Northeast 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.
Which climate drivers affect the weather in the US Northeast?
Measured from seasonal temperature and rainfall in the US Northeast since 1950, with the long-term warming trend removed, no climate driver has a strong or moderate effect here; there are weak links to the AO, the NAO, which may partly be chance. They are listed in the Climate Drivers section of this page.
What extreme weather affects the US Northeast?
NOAA's Storm Events Database recorded 73 damaging weather events in the US Northeast in 2025 - storms, floods, heat, drought and wildfires that killed or injured anyone or did $1M or more of damage - against an average of 69 a year in 2016-2025, with 39 deaths. The deadliest since 1996 was the July 1999 heat wave (4 July 1999, Pennsylvania), which killed 74. GDACS, the UN and European Commission's disaster alert system, issued 0 Major (Red) and 1 Severe (Orange) alerts for the US Northeast in the last 12 months. Live alerts are on this page and on the Extreme Weather tracker.
Where does the climate data for the US Northeast come from?
Climate data for the US Northeast comes from authoritative climate datasets including national meteorological services and peer-reviewed reanalyses, 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 US Northeast climate data cover?
The US Northeast climate profile covers New York, Pennsylvania, Massachusetts, New Jersey and surrounding areas. NOAA Northeast climate region - CT, DE, ME, MA, MD, NH, NJ, NY, PA, RI, VT
How often is the US Northeast climate update refreshed?
The US Northeast 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 US Northeast 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 US Northeast 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 US Northeast experienced?
Major climate events in the US Northeast include The Great New England Hurricane of 1938; Hurricane Agnes (1972); The 1999-2002 Eastern drought; The wet year of 2003; Start of the sustained rise in US heatwave frequency (2010); Hurricane Sandy (Superstorm Sandy) (2012). The Climate History panel on this page lists 46 sourced events and pattern shifts relevant to the US Northeast, the earliest from 1912 - 18 about the US Northeast 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 US Northeast 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. 27 of the 46 entries here are written specifically about the US Northeast, 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.
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