Autumn heatwave and fire warnings hit Bay Area

The National Weather Service warns San Francisco and the surrounding Bay Area about an unseasonal heatwave and dangerous fire conditions all day Thursday, with temperatures reaching the 90s.

“A strong high pressure system will slide down the coastline through the day today, suppressing onshore flow, and resulting in unseasonably warm temperatures,” the federal agency says, issuing a heat advisory from 10 a.m. through 7 p.m. Thursday.

The advisory covers not only San Francisco, but also Daly City, Sausalito, Santa Rosa, South Santa Rosa, Napa, San Rafael, Petaluma, Novato, Rohnert Park, Oakland, Fremont, Hayward, Berkeley, Pacifica, Salinas, Santa Cruz, Watsonville, and Live Oak.

The forecast is not as hot as the summer heatwaves suffered a few months ago—NWS predicts that SF and Oakland could hit a high of 94, with areas like Santa Rosa and San Jose rising to around 91, Walnut Creek 92, and Concord 90.

Although no city is likely to hit triple digits today, across the region daytime highs will range “18 to 24 degrees above seasonal normals” and the heat advisory cautions to be vigilant about the potential dangers of excess heat.

“Heat related illnesses such as heat exhaustion and heat stroke will be possible. People most vulnerable include those who are spending considerable time outdoors, those who do not have air conditioning, young children, the elderly, and those with chronic ailments,” says the warning.

At the same time, a red flag warning remains in effect until 4 p.m. in the North Bay and East Bay Hills, with “strong north to northeast winds and low humidity through early Thursday morning” combined with high temperatures to pose a fire risk.

The Kincaid fire in Sonoma County burned more than 10,000 acres with no containment as of Thursday morning. The Sonoma County Sheriff’s Office ordered evacuations for the area around Geysers Road to Highway 128, Pine Flat Road, and Red Winery Road, as well as evacuation warnings for northern Healdsburg and Geyserville.

The good news is that the same forecasts predict that the heatwave will snap starting early in the evening and continue to cool down through Friday, with winds dying down in the late afternoon in most places.