‘Past the peak:’ Fog cools searing Bay Area

The arrival of dense fog in the Bay Area has signaled relief from the record-breaking heat wave that roasted the region.

On Monday, the National Weather Service downgraded the excessive heat warning to an advisory. The warning, in place for nearly a week, was expected to last through Wednesday night. The advisory is in effect through Friday.

“In a way we are past the peak of our hottest temperatures for the Bay Area,” meteorologist Rick Canepa said. “For the Central Valley, it’s a different story. We’re quite fortunate to have the marine influence.”

Scorching heat began in the Bay Area on July 2. On that day, two records were broken in Marin County.

Weather gauges in Kentfield and San Rafael, the only official National Weather Service reading devices in Marin County, both reached 103 degrees, exceeding the previous highs of 101 set in 1991, according to the weather service.

San Rafael beat another record on July 3 at 100, one degree over the previous record set in 2001, the weather service said.

On the Fourth of July, celebrants roasted under a tie-setting 98 degrees in San Rafael. The previous record was notched in 2013.

While the heat continued on Friday and through the weekend, the highs were far from reaching historic markers.

On Saturday, an unofficial weather gauge in Woodacre recorded a high of 105, Canepa said. Novato recorded 101 degrees. The National Weather Service station at Kentfield had a high of 91, far from the 107-degree record set in 1921. San Rafael hit 92, shy of the 97 record in 1989.

Sunday had similar temperatures. But beginning early Monday, the robust high-pressure ridge that had been in place since last week continued its migration east and west, Canepa said. One byproduct of that were overnight temperatures that fell into the 50s in some areas for the first time in more than a week.

“The high-pressure system is weakening,” Canepa said.

For Monday and Tuesday, coastal Marin will remain in the upper 50s to lower 60s. It will be closer to the mid-80s in San Rafael and along the Highway 101 corridor.

The cooldown will be interrupted in the middle of the week by northerly winds and a slight rebuilding of the ridge in the atmosphere’s upper levels, and temperatures will again rise for two days, Canepa said.

The heat will creep back up to the 90s on Wednesday and Thursday around central Marin, and maybe hit the 70s along the coast.

Still, that uptick won’t be anywhere near as intense as the peak conditions during the heat wave that broke daily records in some cities that were more than a century old, according to the weather service.

The downward trend in temperatures will return Friday through the weekend.

As hot, dry conditions persist, the Marin County Fire Department is reminding residents to remain vigilant about fire preparedness.

Marimar Ochoa, a spokesperson for the department, said with more than 100,000 acres burned across the state already, it’s evident this summer is a going to be a busy fire season. The fire department has more than 150 seasonal firefighters working on the defensible space team, fuels crews and engines.

During last week’s “red flag” fire weather warning issued by the weather service, the department increased the number of on-duty staff, Ochoa said.

The department is reminding residents to stay hydrated and to seek refuge from the sun in cool areas or places with air conditioning.

“Heat-related illness often go up during these prolonged heat events,” Ochoa said.

Residents can sign up for emergency alerts at AlertMarin.org.

Bay Area News Group reporter Rick Hurd contributed to this report.