Record-Breaking Heat Wave Bakes the Bay Area Through Friday

The early-season heat wave engulfing much of California this week will push up temperatures a “full 30 degrees warmer” than the typically cool early spring days the Bay Area is used to this time of year, National Weather Service meteorologists said Monday.

“That`s very unusual any time of year,” meteorologist Dylan Flynn wrote in the agency’s daily forecast discussion for the region. “We’ve seen much hotter days in the Summer and early Fall.”

Forecasters expect the heat wave, brought on by a “remarkably strong ridge” of high pressure building over the Pacific Ocean and meandering toward the coast, to break temperature records, bringing a moderate heat risk through Friday and elevating the chance of grass fires igniting.

The service issued its earliest heat advisory of the calendar year, in effect through Friday at 8 p.m., meaning it will be so hot that the risk of heat illness increases.

“We’ve never issued a heat advisory in March, and it just highlights how impressive this event will be,” said Joe Merchant, a meteorologist with the weather service’s Bay Area office.

On Monday, temperatures could reach into the mid to upper 80s across inland areas such as Livermore, Napa, Santa Rosa, and San José. The ridge will reach its height on Tuesday, bringing temperatures in the interior Bay Area to the mid-90s, with 70- to 80-degree temperatures along the coast.

Forecasters said there’s a strong possibility that the heat wave will break “numerous” daily and even monthly records. This week, Pinnacles National Park could record its earliest 100-degree day of the year — 7 degrees warmer than its March record, Merchant said.

San Francisco could tie its all-time high March temperature on Tuesday at 87 degrees. Merchant also warned people flocking to the beach to remember that while it may be hot outside, the ocean is still frigid.

“Just be careful near the water and know your risks,” Merchant said.

At least two Bay Area cities have already broken heat records. Reaching 85 degrees on Sunday, San Rafael topped its current daily record of 83, set in 1972. Redwood City also topped a daily record of 84 degrees, set in 2004.

Merchant said that day after day of high temperatures will boost the chance of grass fires across the region if a spark ignites.

“It’s been a while since we had widespread rain,” the forecaster said. “If a fire were to start, it’d be tough for the firefighters to fight it in this type of heat. And then, the smoke and haze from a large grass fire would also be impactful across the area because of the stagnant air mass.”

Merchant also encouraged residents to “check on your neighbors and friends” who might be vulnerable to the heat.

But how long will the heat wave last? Flynn wrote that the ridge appears like it will weaken this weekend, but “that doesn`t mean temperatures will drop all the way back to normal.”

As of now, Bay Area residents can expect temperatures to likely cool by about 5 degrees Saturday through Monday.