The National Weather Service has issued a Heat Advisory for Friday for most of the inland Bay Area which was expanded earlier today to include the Santa Cruz Mountains.
High temperatures are expected to be widespread on Friday, with some spots seeing highs of 100 to 105 degrees, and 90-degree temps will be prevalent around the Bay. Much of the Bay is under "moderate" risk for heat exposure, while spots like Cloverdale, Livermore, inland Big Sur, and the Sacramento Valley are expected to see "major" heat impacts.
The cause is a strong high-pressure system building off the West Coast, and the Heat Advisory extends from 11 am to 8 pm Friday, with temperatures expected to cool a bit on Saturday, cooling further on Sunday.
People at the most risk for heat impacts are advised to stay indoors with air conditioning, and anyone venturing outside is advised to stay hydrated and seek out shade.
Yosemite National Park is going to be blistering hot on Friday, with warnings going out about possible 106-degree temps in the afternoon.
San Francisco, meanwhile, and most of the Peninsula will be seeing only "minor" heat impacts — and the current forecast has SF only getting a high of 72 on Friday. So, yes, this is an inland heatwave, but it still may feel quite balmy in parts of the city. And they've gotten forecasts wrong before in situations like these — with SF's marine influence, or lack thereof, sometimes being hard to predict.
⚠️Updated Heat Advisory now includes Santa Cruz Mts for Friday. Temperatures will soar into the 90s with HeatRisk reaching the "Moderate" category. Other interior locations remain the same. #cawx #caheat pic.twitter.com/jwMD64wzkT
— NWS Bay Area 🌉 (@NWSBayArea) May 28, 2025
The Chronicle notes that this heatwave comes after a fairly "unremarkable" weather month in May, in which San Jose has not even seen a 90-degree day yet.
In its Area Forecast Discussion this morning, the National Weather Service warns that winds are going to pick up Wednesday afternoon along the coast due to the "increasing onshore gradient."
By Friday, "impactful heat" arrives, and the weather service notes of the ridge of high pressure, "the airmass associated with the ridge is rather toasty." And they say some areas along the interior Central Coast may end up with a second day of a Heat Advisory.
"Not expecting this to be a record breaking heat event, but some of the hottest temperatures of the year for some locations," the weather service says.
