Tennessee 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

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

1952 was Tennessee's 2nd-driest year (1074 mm, 20% below its 1961-90 average) and also its highest heatwave-day count on record at 41.5. That is the highest heatwave-day count of any state east of the Mississippi in this site's whole US record.

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

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

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, Tennessee averaged +0.95°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

The strongest La Niña of the 1950-present record, part of a multi-year cool phase that also included a second, separate La Niña in 1975-76.

ONI -2.0°C · RONI -1.9°C

NOAA CPCENSO Tracker

The cold winters of 1976-79

1976 is Tennessee'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.

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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

The 1980 heat wave and drought

1980 was Tennessee's 10th-driest year of the 1950-2025 record, with 14.5 heatwave days (15th-highest). Tennessee was among the worst-affected states for heat deaths, though the signal in its annual figures is more muted than in Missouri's or Kansas's.

NOAA NCEI Billion-Dollar Disasters, Linda Hall Library, Karl & Quayle 1981

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

El Niño has only a weak pull on Tennessee's winter rainfall - it is not one of the seven states where ENSO reliably moves it. In 1982-83 Tennessee's winter rainfall was close to its 1961-90 average (+7%), with temperatures +1.9°C. On NOAA's RONI index, which strips out background ocean warming, this is the strongest El Niño since 1950.

ONI +2.1°C · RONI +2.4°C

NOAA CPC, NOAA CPC (2)ENSO Tracker

1988 Midwest drought / Yellowstone fires

1988 was a dry, hot summer across the Midwest, but Tennessee's own year was milder than its neighbours' - 16th-driest of 76 years and 31st-highest for heatwave days. The worst of it sat over the Corn Belt and northern Plains.

NOAA

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 Tennessee's 10th-warmest year in this site's 1950-2025 record, and 1991 its 13th-warmest. 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 Tennessee's own record. 1993, two years after the June 1991 eruption, ranks 23rd-coldest of the 76 years there, though 1996, 1997, 2013 and 2014 have since been colder. A single large eruption can hold temperatures down for two or three years; it cannot reverse the trend.

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Atlantic Multidecadal Oscillation flips to a warm phase

The Atlantic Multidecadal Oscillation flipped to a warm phase in 1995. Atlantic hurricanes reach this far inland mostly as remnants - Helene's floods in east Tennessee in 2024 among them - and warm AMO phases have also been linked to more frequent drought across the central United States. It is a natural cycle of roughly 60-70 years, so it shifts the baseline rather than driving the long-term trend.

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1997-98 El Niño

In 1997-98 Tennessee's winter rainfall was close to its 1961-90 average (+0%), with temperatures +2.5°C - though ENSO's pull on rainfall here is weak. It is often treated as the textbook strong El Niño.

ONI +2.4°C · RONI +2.3°C

NOAA CPC, NOAA NCEIENSO Tracker

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.

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The 2006-08 Southeast drought

2007 is Tennessee's driest year in this site's 1950-2025 record - 29% below its 1961-90 average - and the same year its lowest relative humidity of any year in that record. The two go together: parched ground and dried-out vegetation stop returning moisture to the air, so the humidity that normally hangs over the south-east simply was not there.

NWS, NWS Key West, Florida BRACE, Florida Climate Center

Start of the sustained rise in US heatwave frequency

Tennessee's own Heatwave Days (WSDI) count rose from a 1961-90 average of 7.1 days a year to 12.8 in 2016-25 - a clear rise, though more moderate than the 2.4x averaged across the 50 states.

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

The 2010 Nashville flood

13.57in of rain in 36 hours (new 2-day record, more than double the prior record); $2bn+ damage, 26 deaths. Called a '1,000-year event.'

NWS Nashville

2011 Super Outbreak (Tuscaloosa-Birmingham)

Part of the 27-28 April 2011 Super Outbreak, the largest tornado outbreak in US history. Its tornadoes killed 33 people in Tennessee - the state's deadliest weather event since NOAA's full records began in 1996 - on the same day 243 died in Alabama.

NOAA NCEI

The 2012 drought and heat

Tennessee recorded 26.6 heatwave days in 2012, its 5th-highest on record here, alongside its 2nd-warmest year - but rainfall finished only 19th-driest of 76 years. In Tennessee 2012 is remembered as the heat; the drought's worst conditions sat over the Plains and Corn Belt.

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

Post-2013 acceleration in US temperatures

6 of Tennessee's ten warmest years on record have occurred since 2013, and 8 of the ten since 2000, with 2024 the warmest of all.

NOAA Climate at a Glance

The polar-vortex winter of 2013-14

2014 is Tennessee's 12th-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

In 2015-16 Tennessee's winter rainfall ran +21% against the 1961-90 average, with temperatures +3.0°C - though ENSO's pull on rainfall here is weak. 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.

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. Tennessee's own record is a looser fit - six of its eleven warmest fall in that span, with 2012, 2007, 1999, 1998 and 1990 outside it. Its warmest year is 2024.

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Nights warm faster than days in the South-East US

Tennessee's nights have warmed far faster than its days. Against the 1950-2014 average, the 2015-2025 period runs +1.36°C on overnight minimum temperature but only +0.79°C on daytime maximum - nights warming roughly 1.7 times as fast. The gap between day and night has closed by 0.57°C, the 5th-largest narrowing of any US state.

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

2018: the wettest year on record across the East

2018 was Tennessee's wettest year in this site's 1950-2025 record - 1705 mm, 27% above its 1961-90 average and just 6 mm ahead of 2019 (1700 mm) - a record broken by a whisker.

NOAA NCEI, NOAA Climate.gov, NOAA NESDIS

The 2019 Southeast flash drought

2019 gave Tennessee its 2nd-highest heatwave-day count of the 1950-2025 record (33.7). September 2019 was among the driest on record here, and Nashville had its hottest September ever measured. The year as a whole was not dry at all here - it was Tennessee's 2nd-wettest of 76. A month of heat did the damage, and the annual total never shows it.

NOAA Climate.gov, NOAA NCEI, Wang et al. 2021

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

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.

ONI +2.0°C · RONI +1.4°C

NOAA CPCENSO Tracker

Hurricane Helene

Helene's remnants brought extreme rainfall to east Tennessee on 26-28 September 2024, flooding the Nolichucky and forcing evacuations in Erwin and Greeneville. Like western North Carolina, Tennessee's damage came from a storm that had long since stopped being a hurricane, over terrain that turns tropical rain into flash flooding.

NOAA Climate.gov, World Weather Attribution