The latest Bay Area heat wave is expected to roast the region for a few extra hours before some cooler air starts to enter the area, according to the National Weather Service.
The relentless heat, which settled over the region on Monday, is expected to surpass 100 degrees in several cities and reach the mid-to-high 90s in places where it doesn’t. Even the normally usually cooler spots along the Bay area are likely to be at least in the mid-80s.
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All of it was predicted to be significantly cooler by Friday. Now, the weather service has at least enough doubt about that scenario that it has extended a heat advisory through Friday at 8 p.m. The advisory originally was slated to expire Thursday at 11 p.m.
The East Bay valleys and hills, Santa Clara Valley, Eastern Santa Clara hills, Santa Cruz Mountains, Marin Coastal Range and the North Bay interior valleys and interior all fall under the advisory, as do the San Benito Mountains and interior Monterey County. The advisory does not apply for San Francisco.
“We’re more confident now that the temperatures are going to stay very hot for the next two days,” NWS meteorologist Dial Hoang said. “We’re not expected as much to cool off, especially in the interior areas.”
Forecasts earlier this week indicated the weather service believed temperatures would fall 5-7 degrees in some cities. Now, the predictions indicate the temperature may fall only 2-3 degrees, and Hoang said the overnight air is expected to stay warmer into Friday than originally anticipated.
The hottest areas in the East Bay — Brentwood in Contra Costa County and Livermore in Alameda County — are expected to top out at 102-103 degrees. Walnut Creek, Antioch, and Pleasanton all may surpass 100, according to the the weather service.
In the South Bay, Morgan Hill is forecast to reach 99 degrees and San Jose is forecast to reach 94.
The hot temperatures also are expected to be tinged with mugginess, with the humidity running above 80% in most places, according to the weather service. That development helped to cleanse the air, and two straight days of Spare the Air alerts ended Thursday.
The humidity is also expected to drop significantly on Friday, before temperatures settle into their normal early September pattern on Saturday, Hoang said. A low-pressure trough in the Gulf of Alaska is still gaining momentum, according to forecasters, and it’s expected to bring temperatures below 90 degrees in the hottest spots when it hits the region on Saturday.