Bay Area’s Getting Wet Again, as an Atmospheric River Opens the Door to Winter

National Weather Service forecasters said the first noteworthy atmospheric river of the season will hit the Bay Area this weekend, with the most rain north of San Francisco.

A first storm will begin on Friday as it makes its way down the West Coast. A second storm will follow close behind before moving further south later this weekend or early next week. Forecasters said this weekend’s systems will mostly bring beneficial rain to the region and more rain than snow in the Sierra Nevada.

“People headed to the mountains should be aware that there might be a little snow this weekend, but overall, it’s not looking like a major snowmaker,” said Courtney Carpenter, a warning coordination meteorologist with the weather service’s Sacramento office.

Rainfall totals could amount to about an inch in the North Bay and less than a quarter of an inch in San Francisco and San José.

“Take it as a gateway to winter,” said Rachel Kennedy, a meteorologist with the weather service’s Bay Area office. “Remember to clean out your gutters, so that way when we do get bigger storms later this winter, you’re prepared for them.”

Strong or extreme atmospheric rivers can cause excessive downpours and major flooding. For example, in 2022, a family of atmospheric rivers dumped so much rain over California that multiple levees crumbled from the weight and intensity of the water, destroying hundreds of homes and disrupting life for thousands of people.

“Every year we get strong storms, and those are the ones that really make the headlines,” said Chad Hecht, a meteorologist based in Sacramento with the Center for Western Weather and Water Extremes at the University of California, San Diego’s Scripps Institution of Oceanography.

Hecht categorizes the atmospheric rivers this weekend as potentially weak or moderate if viewed together — but not the extreme storms that can cause major flooding — indicating they would bring mostly beneficial rain. However, they could also be accompanied by wind, freezing temperatures and nuisance flooding.

But exactly where in the region will receive the most rain is still a little up in the air.

“San Francisco is kind of right in that transition period between precipitation and maybe not so much,” Hecht said.

But there is some extra good news that will also fall this weekend: The earlier the rainy season begins, the less likely wildfires will ignite, Hecht said.

“We do like to say fire season ends when you get your first atmospheric river. Unfortunately, it does not play a role in how the water year is going to play out,” Hecht said. “What happens in October does not always mean anything for the rest of the year.”

And for those questioning whether to stay indoors or go outside this weekend, Hecht said, “If you’re going hiking, it’s gonna be a pretty miserable day.”