A weather pattern that’s funneling smoke from fires burning in Northern California and Oregon will bring with it a Spare the Air alert on Wednesday, air officials said.
The Bay Area Air Quality Management District issued the alert, saying the notice was caused by an expected combination of temperatures that could reach 100 degrees in some places, vehicle exhaust and smoke.
Wood burning is prohibited during alerts.
National Weather Service meteorologist Rick Canepa said the region is downstream from the mostly northerly winds that are pulling smoky air toward the Bay Area. The Smith River Complex Fire in Del Norte County and southern Oregon; the Lightning Complex fire on Redwood State and National Parks land; and the Happy Camp fire in Klamath National Forest all have burned more than 10,000 acres.
The weather pattern is supposed reach its peak Wednesday, before a trough developing in the upper atmosphere exerts its influence Thursday.
Forecasters expect the thermometer Wednesday to reach 101 degrees in Brentwood, 99 in Livermore, and 96 in Morgan Hill, generally the hottest places in Contra Costa, Alameda, and Santa Clara counties, respectively. Walnut Creek is expected to reach 97, San Jose 91, Oakland 84 and San Francisco 77.
“Right now, we have high pressure that’s building into the Great Basin area,” Canepa said in explaining the heat. “Once we get past Wednesday, we’re expecting cooling trends with that upper-level trough that’s developing, and that will continue into Friday.”
The cool air is expected to have a cleaning effect on the air, as will the development of coastal clouds and fog as the weekend emerges, according to Canepa. The hottest spots in the region might hit 90 degrees on Thursday, but are not forecast to be higher than 85 on Friday.
Canepa said the change in the weather pattern also could bring coastal drizzle along the Peninsula by early Saturday morning.
The alert came after two days of air advisories. It’s the sixth one issued by the district in 2023.