A bicyclist rides along a path at Robert W. Crown Memorial State Beach in Alameda, Calif., on April 26, 2023.
Douglas Zimmerman/SFGATE
The official National Weather Service gauge in downtown San Francisco is forecast to hit 90 degrees on Thursday, the agency said. If the forecast holds true, the city will see its hottest temperature of the year so far. SF has yet to reach 90 degrees this year.
“We’re trending a little bit warmer,” Dalton Behringer, a forecaster with the weather service’s Bay Area office in Monterey, said. “We have to be careful in our early forecast, we don’t want to overforecast. Based on what happened yesterday, we have a better sense of what’s in the realm of possibility today. Yesterday, it got warm — and slightly warmer than we were expecting.”
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The weather service has been referring to this weather event as a warmup and not a heat wave, and Behringer said the agency will continue to tag it that way as it’s not expected to be a prolonged event.
The warmup comes as a ridge of high pressure centered over the Pacific Northwest was stretched across California on Thursday. While low-pressure systems are associated with cool, wet weather, high pressure brings warming.
On Thursday morning, the air around the Bay Area was stagnant with very little wind, not even a breeze at the coast. Behringer said light offshore winds will develop through the day and these northeasterly winds will usher the hot inland air toward the coast.
“If there is any sea breeze at the coast, it’s going to be weak,” he said. “This may be one of those days where the strength of the ocean breeze matches the strength of the offshore winds and they almost sort of battle each other out.”
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Offshore winds are often associated with high wildfire risk, but Behringer said in this event, the winds will not grow strong enough to raise significant concern about fires.
Temperatures across the Bay Area on Thursday are expected to be in the 80s at the coast, near 90 along the bay front and in the mid- to upper 90s in inland valleys. The hottest locations could break into the 100s.
While the main downtown SF gauge is expected to hit 90, other areas of the city, such as the Mission District, could see even higher temperatures.
“Especially in the city, for those who are going to be outdoors, it’s going to feel stagnant especially if you’re around concrete and buildings,” Behringer said. “It’s going to feel stagnant and gross. You know how it is in the city when there’s no air moving. People are used to the breeze.”
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A heat advisory issued by the weather service goes into effect at 11 a.m. Thursday and continues through 11 p.m. Friday for the South Bay, Santa Cruz Mountains and the bay shoreline, including San Francisco. The agency advised people to stay hydrated and limit outdoor activities in the afternoon and evening. “Never leave kids or pets unattended in vehicles,” the weather service said.
While earlier reports said Friday would be a tad cooler than Thursday, Behringer said the new forecast indicates that Friday will see similar temperatures to Thursday.
Saturday is forecast to be a few degrees cooler than Friday, with locations at the coast in the 70s, areas along the bay front in the mid- to upper 80s and inland valleys in the upper 80s to low 90s. Sunday is expected to bring more cooling, and there’s a chance for light rain on Monday.
