A high-pressure system that has been expanding and thickening while hardly moving finally reached a stage in its migration Friday that allowed National Weather Service forecasters to make a hopeful claim.
“The hottest day of this whole heat wave is going to be Saturday,” NWS meteorologist Nicole Sarment said Friday afternoon. “We’re pretty confident of that.”
The ramp-up to that second peak began Friday, following a slight cooldown on the Fourth of July that was a bit noticeable in the evening but not during the day. Still, that heat broke a 51-year-old Fourth of July record at San Francisco International Airport, where the 87-degree reading was 12 degrees warmer than in 1973.
Temperatures on Friday topped 107 degrees in Livermore, 103 in Concord, 95 in Napa, 94 in San Jose and 93 in Redwood City, according to the weather service. Oakland hit 82 degrees, breaking its previous record of 81 set in 1981. Downtown San Francisco and Half Moon Bay, meanwhile, recorded highs of just 71 and 65 degrees, respectively.
On Saturday, temperatures are expected to be around the same if not a bit warmer.
“Saturday is going to be really, really hot,” meteorologist Joe Merchant said. “Hotter than what we’ve seen.”
By Sunday, it won’t be quite as hot. Then again . . .
“It might cool off by 5 degrees,” Sarment said. “If it goes from 115-110, or from 110-105, can you really tell?”
The heat wave already is one of the longest in Bay Area history, according to weather experts. An excessive heat warning that went into effect Tuesday will stay that way through Wednesday, the longest such warning the weather service said it has ever issued.
“Right now, we’re basically at the center of the high pressure,” Merchant said. “Once it shifts a little further east and south, we’ll start to see the things we normally see, such as cooler air aloft and a steadier, stronger onshore flow. It’s just gonna be a while until we get there.”
A red-flag warning for severe fire conditions remained in place in the East Bay Hills until 9 p.m. Saturday. A similar warning in the Santa Cruz Mountains and the upper elevations of Marin County was removed by the weather service.
Fire crews throughout the state continued to have their hands full with wildfires. In Butte County, Cal Fire made significant inroads on the Thompson Fire, reaching 46% containment on a blaze that has scorched 3,789 acres and forced 28,000 evacuations in that county.
The Toll Fire in Napa County was 50% contained and has burned 41 acres, according to Cal Fire. And the Yolla Fire in Shasta County was 90% contained after having burned 19 acres.
The state’s two largest wildfires were both in Fresno County. The Basin Fire had burned 14,015 acres Friday morning and was 46% contained, Cal Fire said. The June Lightning Complex Fire in Fresno County, was 98% contained Friday morning. Cal Fire said it has burned 10,669 acres.
Crews also had to battle several fires locally that officials said were caused by fireworks. A blaze in Antioch near Hillcrest Drive forced evacuations, and crews in San Jose put out two vegetation fires.
The weather service reminded people that despite the hot conditions, the ocean and river waters remain extremely cold. Water temperatures are running between 50 and 60 degrees, and the shock from that cold water can cause muscles to cramp quickly, officials said.
Staff writer Jason Green contributed to this report.
