Minnesota 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

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, Minnesota averaged +1.24°C warmer across 2006-2025 than across the two decades before the Act, 1951-1970, the 12th-largest rise of the 49 states measured and above their median of +1.09°C. Cleaning the air was right for human health. It also uncovered warming that was already there.

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 1976-77 drought

1976 was Minnesota's driest year in this site's 1950-2025 record - 403 mm, 41% below its 1961-90 average. Water levels fell to record lows, the Mississippi included.

USGS, US GAO, USGS Water Data Labs

The cold winters of 1976-79

1979 is Minnesota's 5th-coldest year in this site's 1950-2025 record. Its first months were the end of the winter of 1978-79, the coldest on record for the contiguous United States and the third brutal winter in a row across the Midwest.

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 gave Minnesota 16.7 heatwave days, its 9th-highest of the 1950-2025 record, alongside its 4th-driest year. Minnesota sat at the northern edge of the ridge, and 1980 is still among its driest years. It is worth noting 1980 ranks only 40th-warmest here by annual mean: a fierce three-month summer barely moves a twelve-month average, which is why a heatwave-days count finds this year and an annual temperature record does not.

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 Minnesota's winter rainfall - it is not one of the seven states where ENSO reliably moves it. In 1982-83 Minnesota's winter rainfall was close to its 1961-90 average (+9%), with temperatures +4.6°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 Minnesota's 7th-driest year (569 mm, 16% below its 1961-90 average) with 21.0 heatwave days, its 7th-highest.

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

Mount Pinatubo erupts

Pinatubo's aerosol veil left a clear mark on Minnesota. 1993, two years after the June 1991 eruption, is Minnesota's 11th-coldest year of the 76 on record, though 1996 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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The Great Flood of 1993 (Mississippi River)

1993 was Minnesota's 9th-wettest year in this site's 1950-2025 record - 799 mm, 18% above its 1961-90 average.

NASA Earth Observatory / NWS

Atlantic Multidecadal Oscillation flips to a warm phase

The Atlantic Multidecadal Oscillation flipped to a warm phase in 1995. It is an Atlantic cycle, but its reach is not confined to the coast: a warm AMO alongside a cool Pacific has been tied to more frequent drought across the western and central United States, including the widespread droughts of 1996 and 1999-2002. 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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February 1996 Arctic outbreak, state record colds

On 2 February 1996 Tower, Minnesota fell to -60°F, a state record that still stands. The cold was not just one morning: 1996 is Minnesota's 3rd-coldest year in this site's 1950-2025 record and its 4th for air-frost days. Extreme cold snaps have become less frequent since, which is one of the clearer local signals of a warming baseline.

NWS La Crosse

1997-98 El Niño

In 1997-98 Minnesota's winter rainfall was close to its 1961-90 average (-4%), with temperatures +6.6°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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2006: a national heat record that lasted six years

2006 is Minnesota's 6th-warmest year in this site's 1950-2025 record, and it stands out sharply on the chart because 2005 and 2007 were 0.7°C and 1.1°C cooler. It was the warmest year ever recorded for the contiguous United States at the time, beating the 1998 El Niño record - though Minnesota was one of only three states that did not reach 90°F on 17 July, the peak day of that summer's heat wave. Nationally 2006 has since been pushed down to 10th, passed by nine warmer years in under two decades.

NOAA NCEI, Science

Start of the sustained rise in US heatwave frequency

Minnesota's own Heatwave Days (WSDI) count rose from a 1961-90 average of 6.5 days a year to 13.0 in 2016-25 - more than doubling, close to the 2.4x averaged across the 50 states.

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

The 2012 drought and heat

Minnesota recorded 27.3 heatwave days in 2012, more than in any other year of this site's 1950-2025 record, alongside its 3rd-warmest year - but rainfall finished only 29th-driest of 76 years. In Minnesota 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

5 of Minnesota's ten warmest years on record have occurred since 2013 - fewer than in most states - but 7 of the ten have come since 2000, with 2024 the warmest of all. The acceleration is clear in Minnesota's data; its year-to-year swings are simply wide enough to spread the warmest years further apart than the national mean does.

NOAA Climate at a Glance

The polar-vortex winter of 2013-14

2014 is Minnesota's 8th-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 Minnesota's winter rainfall ran +36% against the 1961-90 average, with temperatures +4.9°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. In Minnesota the pattern is weaker: only five of its eleven warmest fall in that span, with 2012, 2006, 2005, 1999, 1998 and 1987 outside it. Its warmest year is 2024. The warming is in Minnesota's record; it simply arrives in a different order.

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2019: the wettest year across the Upper Midwest

2019 was Minnesota's wettest year in this site's 1950-2025 record - 906 mm, 34% above its 1961-90 average, beating a mark that had stood since 1977.

Wisconsin State Climatology Office / WPR, Midwestern Regional Climate Center, NWS Green Bay

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