Fall heat wave in Bay Area leaves records behind

A late-fall heat wave that cranked up the temperatures for a few days started to give way Thursday to more typical conditions but not before toppling some decades-old records.

The National Weather Service said the high-pressure bubble that created a week of sunny days and put temperatures in the 70s through much of the region started to move away as a southerly surge of lower pressure migrated up the coast.

“That’s gonna mean a big change to our weather pattern over the next few days,” NWS meteorologist Gerry Diaz said. “You’re gonna see a lot of low clouds, and that sea breeze that keeps the region cool is slowly making its way back into the area.”

That means temperatures are likely to move down into the mid-to-upper 60s as the week draws to a close. They are expected to be in the low 60s and 50s by early next week, he said.

There is no rain forecast, though Diaz said there’s a “slight chance” that areas north of Ukiah could receive a bit of moisture from a northerly system by Monday.

“That’s gonna be way north of the Bay Area,” Diaz said. “So I really don’t see that having any effect there.”

The heat wave was initially expected to bring temperatures into the mid-70s, but it proved even more potent. The weather service said temperatures rose to 80 degrees in Gilroy, a mark that broke by five degrees a record for the city previously set in 1958, according to the weather service.

At San Jose Airport, the high temperature Wednesday of 75 degrees broke the previous mark of 72 set in 1927. In downtown San Francisco, the mercury read 73, two degrees more than the previous high in 1959. Oakland also was 73, breaking a seven-year-old mark.

Along with the high temperatures came less-than-ideal air quality. In areas of San Francisco and Marin County, the air-quality index was higher than 100 early Thursday, according to the Bay Area Air Quality Management District, meaning it was unhealthy for those with breathing problems and other sensitive groups.

Most of the region had AQI readings between 51-100, meaning the air was moderately healthy for everyone. In some areas of the Santa Clara Valley and South Bay, the readings were below 50, or healthy for everyone.

The air quality forecast for the weekend indicated the air quality will remain moderately healthy, though Diaz said the onset of the southerly surge should push out some of the pollution.

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Author: Rick Hurd