The first full day of summer arrived on Friday. Along with it came a blast of heat that’s expected to travel like one of Willie Mays’ 660 home runs — blistering in its force, high with the temperatures and deep in its reach.
Unlike Mays, this force of nature won’t stick around long enough to gain much traction.
A two-day rise in the Bay Area heat will give way to some of the region’s more usual weather by Sunday afternoon, according to the National Weather Service. Until then, brace for a bake.
“The most noticeable change is going to be from Thursday into Friday,” NWS meteorologist Dalton Behringer said. “You’re looking at temperatures that are going to be on average 6-10 degrees warmer than they were 24 hours earlier. But the hottest day is going to be Saturday.”
A heat advisory issued by the NWS for the interior of the East Bay, the Santa Clara Valley, eastern Santa Clara Hills, San Benito Mountains and the interior of the North Bay and Monterey will go into effect at 11 a.m. Saturday and last until 10 p.m.
As the summer solstice — the official onset of summer — came at 12:50 p.m. Thursday, a high-pressure system was building along the interior of the state — as well as nationally. That ridge of high pressure is a thick one that will allow temperatures to build over much of the state’s interior, Behringer said.
The effect of that will be to lift temperatures in much of the Bay Area at least into the high 80s on Friday, while the hottest spots hit the 90s, Behringer said. By Saturday, some cities along the interior could see triple-digits.
Concord is expected to top out at 90 degrees on Friday, as is Livermore. Both are expected to reach 99 degrees on Saturday. In the South Bay, Morgan Hill is forecast to reach 88 degrees on Friday before spiking to 97 on Saturday. San Jose is forecast to max at 82 degrees on Thursday before getting up to 91 on Saturday.
“The good news is that we are still calling this a progressive pattern,” Behringer said. “It’s still moving, so it’ll move out of the region pretty quickly, and it’s still gonna stay pretty comfortable near the water.”
The Bay Area’s marine layer, is expected to fade for a couple of days, though winds will continue to be breezy. San Mateo is expected get up to 73 degrees on Friday and hit 81 on Saturday, according to the weather service. Oakland is forecast to have a high of 71 on Friday and 77 on Saturday, while San Francisco is not likely to escape the 60s on either day.
Come Sunday, the thermometer will be creeping back down, Behringer said. By Monday, “it’ll be 8-10 degrees cooler than you see on Saturday, and that’ll be followed by kind of a normal pattern in the days after that.”
Still, the interior for the rest of the state is expected to stay hot, always a concern for fire crews who are battling to put out a number of wildfires that have burned at least 500 acres of vegetation.
The Sites Fire in Colusa County — where it’s expected to be at least 100 degrees into next week and 106 on Saturday — is only 25% contained and has scorched 19,195 acres (30 square miles) — since starting Monday, according to Cal Fire. Evacuation orders and warnings remain in place.
Fire crews are up to 75% containment on the Point Fire in Sonoma County (1,207 acres burned) and 67% containment on the Aero Fire (5,351 acres) in Calaveras County. Temperatures in Calaveras County are expected to be in the high 90s through Saturday and the low 90s into next week. In Sonoma County, the thermometer is expected to say in the 80s.
The largest fire in Southern California — the Post Fire in Los Angeles and Ventura counties — is 61% contained and hasn’t grown in the past 24 hours. It has burned 15,690 acres.
Forecasters reminded people to stay hydrated in the heat by drinking fluids hourly and not just when it begins to feel hot. Those sensitive to the heat were urged to stay in cool areas, if possible. Safety officials added that children and animals should never be left in the car; heat-related illnesses and death can happen within minutes, they said.
By Sunday afternoon, the region will feel the effect of cooler weather. Behringer said come Monday, temperatures likely will be at least 10 degrees cooler than they were on Saturday.