news and events » news

News Header

News Item

return to News

Unexpected weather ‘decapitated’ California wildfire season, experts say

by Hannah Hagemann and Jack Lee, San Francisco Chronicle |

Remnants of an atmospheric river brought Northern California its first solid storm of the year – rain splattered across the Bay Area and Central Coast, while some parts of Tahoe saw snowfall boosted to above average levels for this time of year.

Despite a historic heat wave in September, weather unexpectedly turned colder and wetter. A rare September storm came after the record temperatures and stopped the fire season in its tracks. October was marked by a deep marine layer that sent fog to all corners of the Bay Area.

“That really made a decisive difference in that it decapitated, if you will, the peak of fire season,” said Daniel Swain, a climate scientist at UCLA and the Nature Conservancy.

This week’s storm was a boon, bringing up to a half a foot to a foot of snow across Tahoe so far. Rains throughout the Bay Area mixed with plunging temperatures have felt winter-like. And weather forecasts signal this is the beginning of a larger pattern of more rain and snow to come throughout November.

So, is Northern California’s fire season officially over?

“As this pattern keeps developing, with more rain, this is pretty much the end,” said Craig Clements, director of San Jose State University’s Wildfire Interdisciplinary Research Center. “And it should be because we're already in November.”

If the weather pattern continues, the fast-moving, hot-burning, severe wildfires emblematic of California’s fire season, will go dormant.

“The upcoming additional precipitation will probably be enough to really kill it off,” Swain said.

October’s foggy weather and November’s rains dampen vegetation, making it difficult for fire to spread. The snow at higher elevations further reduces fire risk by keeping soil moistures high.

“This just really kind of locks it in,” said Clements.

In the Bay Area, the moist and cool weather systems have meant the amount of water stored in vegetation - or fuel moisture - is reaching average levels for this time of year. To Díaz, in a multi-year drought, that signals wildfire risk is low.

The wet weather may seem unusual, but it’s actually typical for California in November, contrary to wildfire seasons in recent years and increasingly extreme weather due to climate change.