The climate for the Northwest and most of the contiguous U.S. has become slightly warmer in the past decade, the National Oceanic and Atmospheric Administration reported Tuesday.
The warming was widespread, according to NOAA’s National Centers for Environmental Information, though Montana and the Dakotas bucked the trend and slightly cooled.
“There are some areas that actually have cooler temperature normals, especially in the spring in the north-central U.S.,” said Michael Palecki, manager of NOAA’s climate normals.
NOAA updates every 10 years what’s considered “normal” weather. Statisticians analyzed temperature and precipitation readings from thousands of weather stations between 1991 and 2020.
NOAA will release the new normals May 4. Palecki and other NOAA officials held a conference call with reporters to hit some highlights.
Because two decades overlap, the new climatic normals aren’t that much different. Still, the new norms likely mean fewer seasons, months and days with temperatures “above normal.”
Annual mean temperatures in Washington generally increased by up to 0.5 degree Fahrenheit, though some places warmed slightly more and some did not change.
Oregon, Idaho and Northern California had a similar pattern, though patches of Southern Idaho warmed by more than 1 degree.
The warming was not uniform throughout the seasons. Normal high temperatures in April and October in much of Washington, Oregon and Idaho will now be slightly cooler than previously.
“Not every month in every location in the U.S. is always warming despite the fact that we generally are warming in our climate,” Palecki said.
Warming shows up more clearly by comparing 1991-2020 temperatures to early 20th century normals, he said. The annual mean temperature has increased in every state since 1901-1930.
“There’s a huge difference in temperatures over time as we go from cooler climates in the early part of the 20th century,” Palecki said. “We’re really seeing the fingerprints of climate change in the new normals.”
Roughly speaking, the eastern half the U.S. is getting wetter, while the western half is getting drier, though there are exceptions.
Western Washington and the Idaho Panhandle became wetter in the past decade, as did Montana and the Dakotas.
Much of Eastern Oregon joined California and the Southwest to form a large region that became drier.
The World Meteorological Organization on Monday released its annual global climate report.
Global mean temperatures in 2020 were approximately 2.16 degrees Fahrenheit above baseline temperatures from 1850 to 1900, according to the report.
Northern Eurasia was especially hot, but some areas were cooler than average, including Western Canada, parts of Brazil, northern India and southeastern Australia.