Sweltering 100-degree temps in the forecast as heat hits Bay Area

Humid, muggy weather is forecast to give way to sweltering heat in parts of the Bay Area on Tuesday, with temperatures expected to reach triple digits.

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The National Weather Service issued a moderate heat advisory lasting from 10 a.m. to 10 p.m. on Tuesday, warning of “widespread high temperatures in the 90s with hotspots reaching the low 100s.”

Among the areas most likely to top 100 degrees are the East Bay Hills, the Santa Clara Valley and parts of the North Bay. The advisory warns the greatest risk is to individuals “sensitive to heat.”

Roger Gass, a meteorologist at the National Weather Service, said the sweltering temperatures are due to a weather pattern affecting much of the U.S.

“We see high pressure building over the western United States and generally over the entire central U.S. that’s resulting in the warming temperatures,” he told SFGATE. “We do expect the warmest locations to be in the interior.”

Temperatures in the region are expected to be 10 to 15 degrees above average, Gass said.

Currently, Walnut Creek is forecast to hit 97 degrees, Concord is expected to reach 99 degrees and the hills near Brentwood are expected to hit 100 degrees.

Other parts of the Bay Area will likely see elevated, if not triple-digit, temperatures. Oakland is expected to reach 82 degrees, San Jose is forecast to reach 94 degrees and downtown San Francisco is expected to reach 78 degrees.

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While the temperature is increasing, humidity is again dipping in the area as the plume of subtropical moisture pulled up from the Gulf of California moves east, Gass said. 

The hot weather won’t last too long, however, as a new weather system moves in from the Pacific Ocean.

“We are seeing an upper level trough of low pressure approaching the Pacific Northwest right now, and that’s going to dig a little bit further south and then start to cool conditions,” Gass said. 

Gass said temperatures will drop overnight into Wednesday and that the new weather pattern will bring breezy conditions to the region through Friday.