Oregon, Washington, California set December heat records

Published 1:30 am Wednesday, January 14, 2026

December was the warmest on record in Oregon, Washington and California, while Idaho had its second-warmest December, according to the National Centers for Environmental Information.

The warm month capped a warm year. Washington had its second-warmest year since record-keeping began in 1895. Oregon and Idaho had their third-warmest years and California its fifth warmest.

The unseasonably mild December defied seasonal forecasts. A La Nina formed in the fall and that normally leads to below-average temperatures in the Northwest. This year, however, ocean temperatures were just barely cool enough to form a weak La Nina.

“That weak La Nina is behaving more like a weak or moderate strength El Nino,” Oregon State Climatologist Larry O’Neill said. “This is what we expect from climate change.”

Warm seas in the North Pacific and off the West Coast likely counteracted whatever force La Nina had, former Washington State Climatologist Nick Bond said.

“I don’t think we can blame it or thank it for very much,” he said.

Weather patterns ushered in warm and moist air and combined with climate change to push up temperatures, Bond said. Average temperatures in Washington were nearly 7 degrees above normal.

“I don’t think the weather patterns that dominated December 2025 can be attributed to climate change,” he said. On the other hand, “there is, for sure, a background warming,” he said.

“We are getting warmer. We understand why. We don’t know exactly how it’s going to turn out,” Bond said.

Nationwide, the U.S. had its fourth-warmest year on record, according to a report released Jan. 13. Temperatures across the U.S. were above average, especially in the western one-third of the country. A region that takes in the West Coast and Rocky Mountain states had its hottest year on record.

La Nina years are typically snowy. But Oregon, Washington and Idaho snowpacks are below average for mid-January, according to the Natural Resources Conservation Service. California’s snowpack on Jan. 13 was exactly 100% of average.

A La Nina typically has its most influence early in the calendar year, but the National Weather Service predicts this one will fade away soon.

“We shouldn’t completely discount the lingering effects of La Nina,” Bond said. “It could help cool us off a bit for the next month.”

Here is a closer look at each state:

Oregon: The average temperature in December was 39.7 degrees, or 7.9 degrees above normal. The previous record was 39.6 degrees set in December 1917.

For the year, the average was 49.8 degrees. Only 2015 and 1934 were warmer.

Washington: The average temperature in December was 37.5 degrees. The previous record for the month was 36.7 degrees set in 1939. Washington also had its fifth-wettest December on record.

For the year, the average temperature was 49.1 degrees, tying 1934 for second-warmest. The record belongs to 2015.

Idaho: The average temperature in December was 33.4 degrees, or 9.5 degrees above normal. It still wasn’t as warm as December 1917. The average temperature that month was 34.1 degrees. Idaho had its sixth-wettest December on record.

The average for the year was 46 degrees. Only 1934 and 2015 were warmer.

California: The record-setting average temperature in December was 49.8 degrees, or 6.7 degrees above average. The previous record was 48.4 degrees set in 2024.

The average for the year was 60.4 degrees. California’s 10 warmest years have occurred since 2014.