Mill Valley could hit 92°F on Wednesday, Sept. 9, as a heat advisory blankets 11 Bay Area counties through Thursday evening.
The National Weather Service (NWS) advisory takes effect at 10 a.m. Wednesday and runs through 10 p.m. Thursday, Sept. 10. Temperatures across the region are forecast to run 10 to 20 degrees above normal, the NWS said, according to Patch.
NWS meteorologist Dial Hoang told KQED the event is shaping up to be "one of the most impactful heating events of this summer," with the Highway 101 corridor in Marin among the hottest zones.
Mill Valley's forecast calls for a high of 88°F on Tuesday, Sept. 8, peaking at 92°F Wednesday before easing to 87°F Thursday. Novato is expected to reach 98°F Wednesday. Coastal areas could climb into the low 90s, while some inland spots may hit triple digits.
The region logged about 10 days of below-normal temperatures before the warming trend that began Tuesday, the NWS said.
Overnight lows in warmer areas are expected to stay in the mid-60s to mid-70s, reducing the usual nighttime relief. NWS forecasters said higher humidity will compound the daytime heat Wednesday and Thursday.
The Bay Area Air Quality Management District (BAAQMD) issued a Spare the Air alert for Wednesday, citing forecast unhealthy air quality from high temperatures and light winds, ABC7 reported. The district said ozone poses particular risks for children, older adults and people with respiratory or heart conditions.
Coastal flooding watch
Separate from the heat, minor coastal flooding is possible around high tide Tuesday evening and again Wednesday along low-lying bayshore areas of Marin County. The San Francisco tidal gauge showed Tuesday's high tide reaching about 1 foot above normal around 9:59 p.m., according to SFGate. Any flooding would likely last about an hour around high tide and affect only the lowest-lying shoreline spots.
Staying safe
The NWS urged residents to stay out of direct sunlight when possible, drink plenty of water and shift strenuous outdoor activities to cooler hours. People working outdoors should take frequent breaks in shade or air conditioning. Pets and children should never be left in parked vehicles, even with windows cracked.
On Spare the Air days, the BAAQMD advises exercising outdoors only during early morning hours.
Temperatures are expected to return closer to normal by Friday, Sept. 11, and into the weekend, the NWS said. Residents seeking cooling resources can call 2-1-1 or visit marincounty.gov for local options.
