San Jose is starting the day mild at about 59°F with clear skies at Mineta San Jose International Airport, but the calm is not going to last. After a sunny climb to about 89°F today, the South Bay is staring down a much sharper spike tomorrow, when a Heat Advisory and a Red Flag Warning will overlap, raising risks for heat-sensitive residents and outdoor workers.
Thursday Heat Advisory
Tomorrow is expected to be the peak of this warmup, with highs near 96°F across the Santa Clara Valley and the hottest inland spots nudging toward triple digits. The game plan is simple: shift strenuous outdoor work to the morning or evening, drink plenty of water, and check in on older neighbors and kids, according to the National Weather Service. The Heat Advisory is in effect tomorrow from noon to 11 PM.
Overnight Winds And Fire Danger
On top of the heat, fire danger will climb overnight. A Red Flag Warning for the interior North and East Bay hills is in effect from 11:00 PM today through 9:00 AM tomorrow. Hot, dry offshore winds are forecast to bring gusts of 35 to 45 mph, with ridgetops possibly seeing gusts over 60 mph. Cal Fire is urging residents to take immediate precautions, including avoiding spark-producing activities, securing loose outdoor equipment, and having an evacuation plan ready, per Cal Fire.
Bayshore Flooding And Beach Hazards
While the hills bake and blow, the shoreline has its own issues. High astronomical tides combined with a long-period southerly swell will bring minor bay flooding to low-lying Bayshore areas starting this evening and again later in the week. The swell, around 4 to 6 feet with a 19 to 21 second period, also raises the risk of sneaker waves and strong rip currents on south and southwest-facing beaches. Stay off jetties and only swim near lifeguards, according to the National Weather Service.
How To Stay Safe
To keep the heat from getting the upper hand, drink water throughout the day, use air-conditioned public spaces if you can, and skip heavy midday exertion tomorrow. Pets and people who are medically vulnerable should be in cooler indoor spots. With the Red Flag conditions in play, avoid open burning and gas-powered yard work until humidity recovers, and follow directions from your local fire agencies. Cal Fire provides additional preparation tips.
Forecasts can change, so check the National Weather Service and local fire agencies for the latest updates before locking in outdoor plans this week.
