Oregon 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 1952 Northwest drought

1952 was Oregon's 6th-driest year on record here - 678 mm, 18% 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 Oregon's 2nd-coldest year in this site's 1950-2025 record, capped by the record-breaking Arctic outbreak of mid-November, when the cold arrived across the Pacific Northwest before trees and crops had hardened off for winter.

Monthly Weather Review (1955), US Forest Service

1958: the Pacific Northwest's warm year

1958 is Oregon's 7th-warmest year in this site's 1950-2025 record. 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, Oregon averaged +0.85°C warmer across 2006-2025 than across the two decades before the Act, 1951-1970 - the 6th-smallest rise of the 49 states measured. The Pacific Northwest warms more slowly than the interior, because the ocean on its western side absorbs and releases heat far more gradually than land does. That restraint is in the annual average only. Oregon's 2021 heat dome took Portland to 116°F, nine degrees above any temperature previously recorded 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 Oregon's driest year in this site's 1950-2025 record - 576 mm, 31% below its 1961-90 average. The western half of this drought caused serious hydropower shortfalls as well as water restrictions.

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 Oregon's winter rainfall - it is not one of the seven states where ENSO reliably moves it. In 1982-83 Oregon's winter rainfall ran +34% against the 1961-90 average, with temperatures +1.3°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 Oregon's coldest year in this site's 1950-2025 record, and one of its driest - 29% below its 1961-90 average. The year ended in a record-cold November across the Pacific Northwest, with days of sub-freezing temperatures and 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 aerosol veil left a clear mark on Oregon. 1993, two years after the June 1991 eruption, is Oregon's 5th-coldest year of the 76 on record and no year since has 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 Oregon'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 Oregon's wettest year in this site's 1950-2025 record - 1,241 mm, 49% above its 1961-90 average, the largest excess of the three states hit. The Willamette crested at 28.6 ft in Portland on 9 February, and volunteers built a temporary plywood wall along the top of the seawall to stop the river entering the city. Over a hundred landslides came down in the Portland area alone.

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

1997-98 El Niño

In 1997-98 Oregon's winter rainfall was close to its 1961-90 average (+8%), with temperatures +0.9°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

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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The 2002 Western drought

2002 was Oregon's 5th-driest year on record here - 666 mm, 20% below its 1961-90 average.

NOAA Drought.gov, NOAA NCEI

Start of the sustained rise in US heatwave frequency

Oregon's own Heatwave Days (WSDI) count rose from a 1961-90 average of 8.0 days a year to 13.1 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

7 of Oregon's ten warmest years on record have occurred since 2013, and 8 of the ten since 2000, with 2015 the warmest of all.

NOAA Climate at a Glance

2015-16 El Niño

In 2015-16 Oregon's winter rainfall ran +33% against the 1961-90 average, with temperatures +1.3°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. Oregon's own record is a looser fit - six of its eleven warmest fall in that span, with 2014, 2004, 2003, 1992 and 1958 outside it. Its warmest year is 2015.

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The West's air gets drier

Oregon's relative humidity has fallen 3.0 percentage points comparing 2015-2025 with 1950-2014 - the 7th-largest fall of any US state - while its annual temperature rose +0.91°C over the same comparison.

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

The 2015 western snow drought

For Oregon, 2015 was its warmest year on record and its highest heatwave-day count (45.6 days). Oregon ran about 6.5°F above average through that winter, and its 1 April snowpack finished roughly 90% below normal - as low as California's.

Mote et al. 2016, NOAA Drought.gov, USDA

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

Oregon's Labor Day Fires, September 2020

Oregon's most destructive fire season on record - five simultaneous megafires driven by an extreme offshore wind event. A peer-reviewed study (Abatzoglou et al. 2021) found these fires burned more Cascades forest than the previous 36 years combined.

Abatzoglou et al. 2021

2021 Pacific Northwest heat dome

Portland hit 116°F on 28 June 2021, beating its previous all-time record by 9°F. 2021 is Oregon's 2nd-highest year for heatwave days in this site's 1950-2025 record. Attribution studies concluded the event would have been virtually impossible without climate change.

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