Washington Climate – Sep 2026September 2026 Update

The 1910 'Big Burn'

Eastern Washington lay at the western edge of the Big Burn, which ran mainly through northern Idaho and western Montana over 20-21 August 1910. Smoke from the roughly 3 million acres burned darkened skies far beyond the fire itself, and was reported as far east as New England.

BAMS, 2013

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 1952 Northwest drought

1952 is Washington's driest year in this site's 1950-2025 record - 706 mm, 35% below its 1961-90 average. This is a north-western drought, separate from the great 1950s drought of the Southern Plains that ran through the same decade.

NOAA NCEI

The November 1955 cold wave

1955 is Washington's coldest year in this site's 1950-2025 record. Its defining moment came in mid-November, when a record-breaking Arctic outbreak arrived before trees had hardened off for winter and killed or damaged large areas of young forest across western Washington.

Monthly Weather Review (1955), US Forest Service

1958: the Pacific Northwest's warm year

1958 is Washington's 3rd-warmest year in this site's 1950-2025 record - and the only one of its warmest years before the 1990s. It followed the strong 1957-58 El Niño, when the whole north-east Pacific ran unusually warm; fisheries scientists called 1957 'the year of warm water'.

NOAA Fisheries, NOAA PSL

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, Washington averaged +0.79°C warmer across 2006-2025 than across the two decades before the Act, 1951-1970 - the 5th-smallest rise of the 49 states measured. That is a real rise, not an absence of one. The Pacific Northwest simply warms more slowly than the interior: the ocean to its west stores heat and releases it gradually, holding coastal air temperatures back in a way no inland state benefits from. Washington's extremes have still moved sharply: in the 2021 heat dome Hanford reached 120°F.

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 Washington's 4th-driest year on record here - 843 mm, 22% below its 1961-90 average.

USGS, US GAO, USGS Water Data Labs

Pacific Decadal Oscillation flips to a warm phase

The Pacific Decadal Oscillation is this region's own ocean rhythm. Its warm phase gives the Pacific Northwest milder, drier winters and a thinner mountain snowpack, and the 1976-77 flip began about two decades of it - long enough to show in the region's salmon runs, which is how the pattern was first identified.

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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 Washington's winter rainfall - it is not one of the seven states where ENSO reliably moves it. In 1982-83 Washington's winter rainfall ran +24% against the 1961-90 average, with temperatures +1.8°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

1985: the cold, dry year and the November freeze

1985 is Washington's 2nd-coldest year in this site's 1950-2025 record, and one of its driest - 30% below its 1961-90 average. November 1985 was Seattle's coldest November on record by more than 3°F, with days of sub-freezing temperatures and repeated snow.

ClimateStations.com, University of Washington (Cliff Mass)

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 cooling is only faintly visible in Washington's own record. 1993, two years after the June 1991 eruption, ranks 17th-coldest of the 76 years there, though 2011 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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1992: a warm El Niño year in the Northwest

1992 is Washington's 4th-warmest year in this site's 1950-2025 record, even though Pinatubo was cooling the planet that year. It followed the 1991-92 El Niño, and El Niño winters here tend to run warmer and drier than normal, with a thinner mountain snowpack.

Oregon Explorer, Western Regional Climate Center

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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The February 1996 Pacific Northwest floods

1996 is Washington's wettest year in this site's 1950-2025 record - 1,396 mm, 29% above its 1961-90 average. Warm rain arriving on 6 February fell onto fresh snow and melted it, releasing both at once; every area west of the Cascades took at least seven inches of rain and the mountains over twenty. 1997 came in 6th wettest, so the state had two exceptional years back to back.

NOAA Climate Prediction Center, USGS Oregon remembers the 1996 flood, Oregon Encyclopedia

1997-98 El Niño

In 1997-98 Washington's winter rainfall was close to its 1961-90 average (-2%), with temperatures +1.5°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 flipped back to a cool phase around 1998-99. For the Pacific Northwest a cool phase favours cooler, wetter winters and a deeper mountain snowpack - the opposite of the two decades before.

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2004-05: Washington's warm year and snow drought

2004 is Washington's 7th-warmest year in this site's 1950-2025 record. The warmth carried into the winter of 2004-05, when much of the precipitation fell as rain rather than snow; the mountain snowpack finished 3rd-lowest on record and the state declared a drought in 2005.

Washington Department of Ecology

Start of the sustained rise in US heatwave frequency

Washington's own Heatwave Days (WSDI) count rose from a 1961-90 average of 8.7 days a year to 14.5 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

Post-2013 acceleration in US temperatures

6 of Washington's ten warmest years on record have occurred since 2013, and 7 of the ten since 2000, with 2015 the warmest of all.

NOAA Climate at a Glance

The Oso landslide

At 10:37 on 22 March 2014, a rain-soaked hillside above the North Fork Stillaguamish River near Oso, Washington, collapsed. Some 18 million tons of sand, mud and debris crossed the valley at around 40 mph, burying the Steelhead Haven community and State Route 530. It killed 43 people - the deadliest landslide in US history.

USGS, NOAA NCEI Storm Events

2015-16 El Niño

In 2015-16 Washington's winter rainfall ran +33% against the 1961-90 average, with temperatures +1.9°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 Washington the pattern is weaker: only five of its eleven warmest fall in that span, with 2014, 2004, 1998, 1992, 1987 and 1958 outside it. Its warmest year is 2015. The warming is in Washington's record; it simply arrives in a different order.

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Washington's largest wildfire season on record, 2015

1,137,664 acres burned (Jun-Sep 2015), amid historic regional drought - the largest Washington fire season on record, called a likely 'harbinger' of future conditions.

Wikipedia

The West's air gets drier

Washington's relative humidity has fallen 2.3 percentage points comparing 2015-2025 with 1950-2014 - the 8th-largest fall of any US state - while its annual temperature rose +0.89°C over the same comparison. Washington's is the smallest fall of the eight, but it is still larger than any state outside the West.

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

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

2021 Pacific Northwest heat dome

Seattle reached 108°F on 28 June 2021, beating its previous all-time high of 103°F; Hanford, near the Tri-Cities, hit 120°F, the highest temperature ever recorded in the state. 2021 ranks 4th for heatwave days in Washington's 1950-2025 record here - but only 11th for annual mean temperature, which is the point: a few days this far outside the historical range do not move a yearly average, and a yearly average is the wrong instrument for finding them.

Philip et al. 2022, NOAA Climate.gov, USDA Climate Hubs

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