The second primary heat wave of the summer is starting to take shape across the Bay Area, and forecasters expect this one will be hotter and longer than the first. On top of the heat, plummeting humidity will add to the fire danger. The National Weather Service issued an excessive heat warning to cover the interior Bay Area and Central Coast on Saturday and Sunday. A warming trend will be noticeable in a few places Wednesday and Thursday before intensifying universally over the weekend. (NWS Bay Area) “Temperatures gradually increase through this week, peaking over the weekend with highs well into the 90s and up to 110 for inland valleys,”
NWS Bay Area forecasters wrote in a Tuesday briefing. “With no major offshore winds expected, the marine layer will likely remain intact along the coast, keeping afternoon highs generally in the 70s.” Even San Francisco will likely see heat risks over the weekend, with the Peninsula and Santa Cruz County rising moderately. Significant heat risks and very low humidity are forecast in the North Bay, East Bay, and South Bay, along with Monterey and San Benito counties. Overnight cooling will be limited, especially in the hottest regions. (NWS Bay Area) “This leads into a weekend that can be hazardous to your health if you are unprepared,” forecasters said Wednesday. “Not only will there be triple-digit heat for the inland areas, but overnight relief from the heat could be stunted as lows only fall into the 60s and 70s in the areas of most concern — making this heat event feel more like a marathon than a few sprints of hot temperatures.” Find out what’s happening in Menlo Park-Atherton with free, real-time updates from Patch. Cloverdale, Concord, Livermore, and Santa Rosa are among the places likely to hit triple digits by the weekend, and a few daily heat records may fall.
Northern portions of Napa and Sonoma counties could see temperatures soaring as high as 110 degrees. In addition to the elevated health risks for pets, livestock, heat-sensitive groups, and people without access to adequate cooling, very low relative humidity will create significant fire hazards. “High temperatures will cause drying of fuels, and with no rainfall expected, fire danger will start to increase,” forecasters said. “Minimum daily [relative humidity] values in the interior will drop to the low 20s to teens.” (NWS Bay Area) There are still a few moving parts in the forecast, and the National Weather Service is working to refine a few areas of uncertainty, encouraging community members to keep a close eye on changes to the forecast each day. “We continue to monitor the upcoming warming trend into the weekend, fine-tuning the upcoming heat forecast and its associated impacts,” NWS Bay Area wrote Wednesday. “There is still some uncertainty regarding just how warm it will get in areas such as the Santa Clara Valley (and other “transitional” areas between coastal and further inland regions), so be sure to stay updated with the forecast as well as any upcoming changes.” While the worst of the heat should be contained to the weekend, long-term outlooks still favor unseasonably warm temperatures sticking around across the state through next week.