San Francisco's spring seasons are getting warmer
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Spring is getting warmer overall and featuring more unusually hot days in most U.S. cities, including San Francisco, a new analysis finds.
Why it matters: Warmer springs can cause early snowmelt, which can imperil summer water resources, heighten wildfire risks and worsen allergies, among other effects.
Driving the news: Nonprofit climate research and communications organization Climate Central examined 55 years of U.S. temperature data for 241 cities and found that the meteorological spring season of March through May has warmed by a national average of 2.4°F.
- The group found that 97% of the 241 cities analyzed saw a warming trend for the season.
Zoom in: All 58 of California's counties experienced an increase in average spring temperatures from 1970 to 2024.
- The city of San Francisco has seen average seasonal temperatures spike by 2.7°F since 1970.
- It now has an average of 20 more days with hotter-than-normal spring temperatures, per Climate Central.
Between the lines: The spring warming in the U.S. is taking place in tandem with increasing temperatures around the world due to human emissions of greenhouse gases from burning fossil fuels.
- In California, spring snowmelt has also increasingly occurred earlier in the year, according to the state's air resources board.
The big picture: The cities that have warmed the most since 1970 were Reno, Nevada, which has seen average seasonal temperatures spike by 6.8°F, followed by El Paso, Texas at 6.4°F and Las Vegas at a seasonal average temperature increase of 6.1°F.
- While the Southwest is the region seeing the fastest-warming spring, the fall actually outranks spring for the fastest-warming season in much of the Southwest and West.
- Winter is the fastest-warming season for much of the Central and Eastern U.S., along with Alaska.
Yes, but: One region of the U.S. has seen some cooling during spring.
- It stretches from northern Montana into North and South Dakota as well as a sliver of Minnesota.