Maine 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 summer of 1953

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.

Northeast Regional Climate Center, LIFE

The 1962-66 Northeast drought

1965 was Maine's 2nd-driest year on record here - 811 mm, 25% below its 1961-90 average. It was not one dry year but five: 1962-66 as a whole averaged 11% below that baseline. Maine sits at the northern edge of the drought and was the least severely hit of the New England states, though 1965 still ranks 2nd-driest in its own record.

USGS, Seager et al. 2012, NYC Emergency Management

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, Maine averaged +1.25°C warmer across 2006-2025 than across the two decades before the Act, 1951-1970, the 11th-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

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

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 Maine's winter rainfall - it is not one of the seven states where ENSO reliably moves it. In 1982-83 Maine's winter rainfall ran -12% against the 1961-90 average, with temperatures +2.8°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

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 Maine's 15th-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 Maine's own record. 1993, two years after the June 1991 eruption, ranks 18th-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.

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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.

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1997-98 El Niño

In 1997-98 Maine's winter rainfall ran +22% against the 1961-90 average, with temperatures +2.9°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

The Ice Storm of 1998

Maine took the worst of the January 1998 ice storm: 1-3 inches of ice accreted over days of freezing rain, 900,000 Mainers lost power, all 16 counties were declared federal disaster areas and damage reached about $320m. It was called a 100-year event at the time.

USDA Forest Service

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 1999-2002 Eastern drought

2001 is Maine's driest year in this site's 1950-2025 record - 758 mm, 30% below its 1961-90 average. It was not one dry year: 2001 and 2002 together averaged 17% below that baseline. Maine's wettest year on record, 2005, is only four years later - the two extremes of its whole 76-year series inside five years.

USGS New England Water Science Center, Vermont State Climate Office, NOAA Drought.gov

The October 2005 Northeast floods

2005 is Maine's wettest year in this site's 1950-2025 record - 1,564 mm, 44% above its 1961-90 average, and the largest single-year excess of any state those floods reached. Brunswick took nearly 12 inches in the October storms alone, when the remnants of Tropical Storm Tammy stalled over interior New England.

USGS, US Army Corps of Engineers

2006: a national heat record that lasted six years

2006 is Maine's 5th-warmest year in this site's 1950-2025 record. It was the warmest year ever recorded for the contiguous United States at the time, beating the 1998 El Niño record - and it has since been pushed down to 10th nationally, passed by nine warmer years in under two decades.

NOAA NCEI, Science

Start of the sustained rise in US heatwave frequency

Maine's own Heatwave Days (WSDI) count rose from a 1961-90 average of 2.1 days a year to 5.5 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 Northeast's record summer of 2010

2010 gave Maine more heatwave days than any other year in this site's 1950-2025 record (19.5), alongside its 2nd-warmest year overall. Maine also recorded fewer air-frost days in 2010 than in any other year of this record. The Northeast as a whole had its warmest January-August on record that year, 3.4°F above average.

NOAA Climate.gov, NOAA NCEI, Northeast Regional Climate Center

Post-2013 acceleration in US temperatures

5 of Maine's ten warmest years on record have occurred since 2013 - fewer than in most states - but 8 of the ten have come since 2000, with 2024 the warmest of all. The acceleration is clear in Maine'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

2015-16 El Niño

In 2015-16 Maine's winter rainfall ran +31% against the 1961-90 average, with temperatures +4.8°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. Maine's own record is a looser fit - six of its eleven warmest fall in that span, with 2012, 2010, 2006, 1999 and 1998 outside it. Its warmest year is 2024.

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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