It wasn’t a downpour. But it wasn’t just a light sprinkle. And a few areas in the mountains actually got a decent amount.
The rain that fell Sunday across the Bay Area ranked as the highest precipitation total for any day in nearly six months.
That’s not unusual. Very little rain falls most years in summer in California. Nevertheless, the soggy Sunday was a reminder that autumn is here and the state’s winter rainy season has begun.
San Francisco received .19 inches Sunday — not a lot by winter storm standards. But the last time more fell in a single day was on May 5, when the city received .54 inches.
Oakland similarly saw .19 inches, the most since May 6, when .22 inches fell.
The storm came ashore mostly in the Sonoma area, so rain totals were lower farther south. San Jose received .07 inches Sunday, slightly less than the .08 that fell Sept. 30. The last time significantly more fell in the Bay Area’s most populous city was May 5, when .15 inches arrived.
A few higher-elevations spots got very wet, with 2.34 inches falling on Mount Tamalpais in Marin County, and 1 inch coming down in the Santa Cruz Mountains and East Bay Hills.
“This is the kind of rain we like to see,” said Dalton Behringer, a meteorologist with the National Weather Service in Monterey. “There was no flooding. But it was enough to wet the ground, and wet the trees and the grass, reducing fire risk.”
After a few dry and cooler days, the next chance for rain will be Thursday night, Behringer said. That’s likely to be less than Sunday’s and more focused on the North Bay. The outlook otherwise is dry for the rest of the month, including Halloween.
California’s severe three-year drought ended last winter when more than 30 atmospheric river storms filled reservoirs around the state and dumped the most snow in the Sierra Nevada of any winter in 40 years. Bay Area rainfall totals also were robust.
Over the 2022-23 “water year” that ended on Sept. 30, San Francisco received 33.87 inches — 148% of normal. That was the 14th wettest year of the 174 years since 1849 when records began, and the most of any year in the past 25 years, since 1997-98, when 46.56 inches fell during a soaking El Niño winter that brought widespread flooding across the state.
Strong El Niño conditions are shaping up now in the Pacific Ocean, with warmer-than-average ocean temperatures along the equator off South America. Although El Niño conditions increase the chances of a wet winter in Southern California, historically, they are not a guarantee of a wet winter in the Bay Area or other parts of Northern California.
“It’s a tossup,” said Behringer. “If you look back at the El Niño years you’ll find severe droughts and very wet years here. The signal is not very strong.”
October so far has been mediocre in terms of rainfall totals. Although far Northern California is off to a wet start, with Eureka at 138% of its historical average for October, even with Sunday’s rain, Santa Rosa was at 63% of normal for the month, and San Francisco and San Jose were at 33%. Los Angeles hasn’t had any rain in October.
“We are below normal,” Behringer said. “But it’s October and we are just starting the winter season.”
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48-hour rainfall totals, ending at 1 pm Monday, in inches
Mount Tamalpais 2.34
Ben Lomond 1.06
Tilden Park 1.06
La Honda .70
Santa Rosa .58
Big Sur .31
Oakland .22
Mount Diablo .20
San Francisco .19
Fremont .12
San Jose .10
Mountain View .02
(Source: National Weather Service)