Bay Area Faces a Weather ‘Quadfecta’: Heat, Fire Risk, Flooding and Powerful Waves

On Wednesday, temperatures will range from the 80s to 90s in inland areas, with the warmest spots reaching the triple digits, including Concord, Napa and Sonoma. Forecasters expect the ridge to keep the marine layer at bay overnight.

By Thursday, meteorologists forecast temperatures to soar into the 90s or low 100s in inland valleys, including Santa Rosa and San José. The warmest spots — in rural Contra Costa County — could reach around 105 degrees. Temperatures across the Bay will range from the 80s to mid-90s.

Forecasters have also issued a heat advisory from noon to 11 p.m. Thursday for the North Bay, the Sonoma coastal range, the East Bay, the Santa Clara Valley and the San Francisco Bay shoreline.

The current forecast shows a slight cooling trend on Friday, though forecasters said they’ll continue to look out for “heat headlines,” particularly inland in the East Bay. Because of the short duration, Bain said forecasters aren’t calling it a heat wave.

“As of now, this week’s warmth is not going to be like the heat events that we had earlier this year, where we had multiple days of warmth; this will be maybe two days at most,” Bain said.

As for how long the heat will last, Bain said the marine layer could return by Sunday, pushing away the high pressure that is causing the heat.

Still, the “combination of the hot, dry, and windy conditions” has led the weather service to issue a red flag warning for the North and East Bay interior and mountain areas from 11 p.m. Wednesday through 9 a.m. Thursday. Fire weather conditions may also be prevalent in mountain areas in Santa Clara County.

Overnight, forecasters said to expect strong north-to-northeast winds of up to 45 mph in mountain areas; gusts of 60 mph or higher are possible at the highest elevations. The winds will help lower relative humidity, and “result in critical fire weather conditions where any fires that start could take hold and spread rapidly,” forecasters wrote in their daily forecast discussion.

The weather service also expects normal high astronomical tides with about a half a foot of surge. This will likely result in minor flooding in low-lying parts of the Bay Area on Wednesday evening. The hardest-hit areas could be in the North Bay, particularly Marin County. Forecasters expect the high tides to expand across the rest of the Bay Area on Thursday.

As a result, the weather service issued coastal flood advisories starting at 6 p.m. Wednesday for the North Bay, and at 7 p.m. Thursday for the rest of the San Francisco Bayshore.

Forecasters expect the San Francisco tidal gauge to read around 7 inches above normal at around 8 p.m. Wednesday, 1.2 feet above normal around 9 p.m. Thursday, and 1.5 feet above normal around 9:30 p.m. on Friday. Coastal flood advisories will likely remain in effect into the weekend as high tides persist.

And finally, meteorologists expect an increased risk of potentially dangerous sneaker waves and rip currents along southwest-facing beaches on the Pacific Coast this week. As a result, NWS has issued a beach hazards statement for the coast along the North Bay as well as San Mateo and Santa Cruz counties through 5 a.m. Thursday.

Sneaker waves can run up the beach farther than smaller waves and catch beachgoers by surprise and sweep them out into the water.

“People should care because, as the name implies, sneaker waves happen very suddenly,” Bain said. “Pay attention because sneaker waves aren’t always huge waves. Be smart and be aware.”