A Wednesday afternoon that was expected to feel about the same as the one that preceded it 24 hours earlier spread its power just a bit further in what the National Weather Service said would be its most formidable day of a brief Bay Area heat wave.
A heat advisory already in effect for the East Bay Bay hills and interiors; the Santa Clara Valley and eastern Santa Clara hills; San Benito Mountains and the southern Salinas Valley and Monterey Interior was extended to include the Santa Cruz Mountains. The advisory remains in effect through the end of Thursday.
“That’s really the only thing that’s different than (Tuesday),” NWS meteorologist Dalton Behringer said. “The temperatures and the overall conditions at the beach and the warm temperatures overnight all are about the same.”
A beach hazard also remained in effect along the Bay Area and Big Sur coasts — though not along the Santa Cruz coast — with waves expected to break between 8 and 15 feet high.
Behringer said forecasters were certain the peak of the heat wave was Wednesday, saying a small ridge of high pressure that has built into a small bubble will start to depart the area, replaced by a bit of lower pressure coming from the other side.
What they didn’t expect was the thermometer to run as hot as it did on Tuesday, when temperatures ran 99 degrees in Concord, 98 on the Altamont Pass, 95 in Livermore, 89 in San Jose, 88 in Oakland and 83 in Hayward. All of those were among the top 10 hottest spots in the region.
At noon on Thursday, temperatures in Livermore read 94 degrees on the way to an expected 100. Concord temperatures read 92 degrees and also was forecast to hit 100. The San Jose reading was 91 and supposed to reach 95.
By Thursday morning, a significant amount of marine layer will be back, and by Friday it may be back in full, Behringer said, adding that its re-appearance after a two-day absence will act in the usual way.
“If you’re near the shorelines, you’re going to really feel it,” he said, adding that Thursday may feel similar to Monday, when temperatures climbed into the mid to high 80s. By Friday, “it will still be above normal a few degrees but significantly cooler than we’ve seen this week. But on the shore — it’ll cool off at least 10 degrees.”
In Oakland, temperatures were expected to peak at 82 on Wednesday but only 68 on Thursday. In San Francisco, forecasters anticipated a high of 79 on Wednesday and a high of 64 on Thursday.