Louisiana Climate – Sep 2026September 2026 Update

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.

Smithsonian Global Volcanism Program, Alaska Volcano Observatory, National Park Service, Oman et al. 2005

Louisiana's coastal wetland loss

USGS: Louisiana has lost ~1,900 sq mi of coastal wetlands since 1932, peak loss >100km²/yr in 1956-1978.

USGS

Post-WWII industrial expansion begins

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'.

Klimont et al. 2013

The 1950s drought

1954 was Louisiana's driest year in this site's 1950-2025 record - 1009 mm, 31% below its 1961-90 average.

NOAA Drought.gov, NOAA Climate Program Office, Texas Water Development Board

How much ENSO really controls Louisiana's winter rain

Across the fourteen ENSO events in this site's record, Louisiana's winter rainfall followed the index in five of six El Niños and seven of eight La Niñas. The index explains about 15% of the year-to-year variation in Louisiana's December-February rainfall. The extremes: 1982-83 came in +73% against the 1961-90 average, 1999-00 -52%.

NOAA CPC Oceanic Nino IndexENSO Tracker

Agung eruption

Agung's eruption in Bali put a veil of sulphate haze into the stratosphere that cooled global temperature by about 0.3°C over 1963-66.

Smithsonian Global Volcanism Program, NOAA Global Monitoring Laboratory

Hurricane Camille

Camille passed just east of Louisiana on 17 August 1969, sparing New Orleans the worst but flooding the Mississippi delta parishes with surge. The storm's catastrophic landfall came ashore in Mississippi; Louisiana's own defining hurricane arrived 36 years later as Katrina.

NWS Mobile, Mississippi Encyclopedia, Encyclopedia Virginia

US Clean Air Act

The 1970 Clean Air Act set strict national standards for sulphur dioxide and particulates, and American skies got measurably cleaner over the decades that followed. 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. Measured here, Louisiana averaged +0.92°C warmer across 2006-2025 than across the two decades before the Act, 1951-1970, against a median of +1.09°C across the 49 states whose records reach back that far. Every one of them warmed. The range runs from +0.66°C in Oklahoma to +1.67°C in Alaska, so the question a state's own chart answers is not whether it warmed, but by how much.

US EPA

The 1973-74 La Niña

Globally this was a strong La Niña in the middle of a sustained multi-year cool phase. In Louisiana it showed up as winter rainfall 35% above the 1961-90 average - its 6th-largest ENSO rainfall swing on record.

ONI -2.0°C · RONI -1.9°C

NOAA CPCENSO Tracker

The Mississippi flood of 1973

1973 was Louisiana's 2nd-wettest year on record here - 1851 mm, +26% against its 1961-90 average.

USGS Professional Paper 937, NWS St. Louis

The 1975-76 La Niña

Louisiana's winter rainfall ran 42% below its 1961-90 average in the 1975-76 La Niña - its 5th-largest ENSO rainfall swing on record.

ONI -1.6°C · RONI -1.1°C

NOAA CPCENSO Tracker

The cold winters of 1976-79

1976 is Louisiana's coldest year in this site's 1950-2025 record, and 1979 its 4th-coldest - the two ends of 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 1978-79 was the coldest winter on record nationally.

Illinois State Water Survey, Missouri Climate Center, Monthly Weather Review (1978), Wikipedia

Pacific Decadal Oscillation flips to a warm phase

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.

Learn more →

Global SO2 emissions peak

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.

Klimont et al. 2013

El Chichón eruption

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.

Smithsonian Global Volcanism Program

1982-83 El Niño

Globally this was the strongest El Niño since 1950 on NOAA's RONI index, which strips out background ocean warming. In Louisiana it showed up as winter rainfall 73% above the 1961-90 average - its largest ENSO rainfall swing on record.

ONI +2.1°C · RONI +2.4°C

NOAA CPC, NOAA CPC (2)ENSO Tracker

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.

Zhong et al. 2023

1990-91: mild winters and warm years

1990 is Louisiana's 11th-warmest year in this site's 1950-2025 record. Mild winters did most of it: January-February 1990 was the warmest start to a year the contiguous US had recorded, a record that stood until 1998.

News & Record / AP (1991), NOAA NCEI

Mount Pinatubo erupts

Pinatubo's cooling is only faintly visible in Louisiana's own record. 1993, two years after the June 1991 eruption, ranks 13th-coldest of the 76 years there, though 2014 has since been colder. A single large eruption can hold temperatures down for two or three years; it cannot reverse the trend.

Learn more →

Hurricane Andrew

After devastating south Florida, Andrew crossed the Gulf and made a second landfall in south-central Louisiana on 26 August 1992, still a major hurricane. Louisiana's damage was severe but far short of Florida's - and far short of what Katrina would do to the state thirteen years later.

NOAA NESDIS, National Park Service

Atlantic Multidecadal Oscillation flips to a warm phase

The Atlantic Multidecadal Oscillation flipped to a warm phase in 1995, and for the Gulf coast that has meant a more active hurricane season: the warm phase since includes Katrina and Rita in 2005, Harvey in 2017 and Ida in 2021. It is a natural cycle of roughly 60-70 years, so it shifts the baseline rather than driving the long-term trend.

Learn more →

1997-98 El Niño

Globally this was the strongest El Niño ever measured by the raw ONI index. In Louisiana it showed up as winter rainfall 54% above the 1961-90 average - its 2nd-largest ENSO rainfall swing on record.

ONI +2.4°C · RONI +2.3°C

NOAA CPC, NOAA NCEIENSO Tracker

The 1999-2001 La Niña

Louisiana's winter rainfall ran 52% below its 1961-90 average in the 1999-2000 La Niña - its 3rd-largest ENSO rainfall swing on record.

ONI -1.5°C · RONI -1.6°C

NOAA CPC ONI

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.

Learn more →

Hurricane Katrina

Katrina made its Gulf landfall near Grand Isle on 29 August 2005 as a Category 3 with winds near 127 mph. The storm surge overwhelmed the levee system and about 80% of New Orleans flooded, in places for weeks. Louisiana recorded 341 direct deaths, more than any other state. NOAA's analysis finds climate change increased Katrina's rainfall and surge, and that the same storm in a 1900-era sea level would have done 15-60% less damage.

NOAA NHC, NWS Mobile, Climate Signals

The 2010-2012 La Niña

Louisiana's winter rainfall ran 43% below its 1961-90 average in the 2010-11 La Niña - its 4th-largest ENSO rainfall swing on record.

ONI -1.6°C · RONI -1.6°C

NOAA CPC ONI

Start of the sustained rise in US heatwave frequency

Louisiana's own Heatwave Days (WSDI) count rose from a 1961-90 average of 3.4 days a year to 18.9 in 2016-25 - more than a fivefold increase, among the steepest anywhere in the United States.

World Bank CCKP (CCKP), NOAA Climate at a Glance

The 2012 drought and heat

2012 was Louisiana's 4th-warmest year, but neither exceptionally hot (15th-highest for heatwave days) nor exceptionally dry (51st-driest of 76 years). The drought that made 2012 notorious nationally had its worst conditions over the Plains and Corn Belt, and largely passed Louisiana by.

NOAA NCEI, Summer 2012 Drought Update, NOAA NCEI, Drought

Post-2013 acceleration in US temperatures

7 of Louisiana's ten warmest years on record have occurred since 2013, and 8 of the ten since 2000, with 2023 the warmest of all.

NOAA Climate at a Glance

The polar-vortex winter of 2013-14

2014 is Louisiana's 7th-coldest year in this site's 1950-2025 record. In early January 2014 the polar vortex slipped south and Arctic air spread across most of the country, and the cold returned in waves into March.

Wikipedia, CBS NewsPolar Vortex Tracker

2015-16 El Niño

Globally this was tied with 1997-98 as the strongest on the raw ONI index. In Louisiana it showed up as winter rainfall 16% below the 1961-90 average - its 10th-largest ENSO rainfall swing on record.

ONI +2.6°C · RONI +2.3°C

NOAA CPCENSO Tracker

2015-2025: the eleven warmest years on record

Globally, the eleven warmest years on record have all happened since 2015. Louisiana's own record is a looser fit - seven of its eleven warmest fall in that span, with 2012, 1999, 1998 and 1990 outside it. Its warmest year is 2023.

Learn more →

Nights warm faster than days in the South-East US

Louisiana's nights have warmed far faster than its days. Against the 1950-2014 average, the 2015-2025 period runs +1.42°C on overnight minimum temperature but only +0.76°C on daytime maximum - nights warming roughly 1.9 times as fast. The gap between day and night has closed by 0.65°C, the largest narrowing of any US state.

NOAA Climate at a Glance, World Bank CCKP (CCKP)

Hurricane Harvey

After flooding Houston, Harvey made a second landfall near Cameron, Louisiana on 30 August 2017, bringing serious flooding to the south-west of the state. Louisiana escaped the worst of a storm whose US rainfall record - 60.58 inches - was set just across the Texas line at Nederland.

World Weather Attribution, van Oldenborgh et al. 2017, Risser & Wehner 2017, NOAA Climate.gov

Low-sulphur shipping fuel rule (IMO 2020)

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.

Gettelman et al. 2024

2023-24 El Niño

Globally this was a strong El Niño, the first since 2015-16. In Louisiana it showed up as winter rainfall 19% above the 1961-90 average - its 8th-largest ENSO rainfall swing on record.

ONI +2.0°C · RONI +1.4°C

NOAA CPCENSO Tracker