Overview

• The National Weather Service has a Heat Advisory in effect from 11 a.m. to 7 p.m. for San Francisco, the East Bay and the Santa Clara Valley.
• Inland valleys are forecast to reach the upper 90s to low 100s as coastal and urban areas climb into the 80s and 90s, likely marking 2025 highs for San Francisco, Oakland and San Jose.
• Forecasters attribute the surge to a high‑pressure ridge and offshore winds that suppress the marine layer and raise wildfire risk.
• The NWS warns of heat‑illness hazards and urges hydration, light clothing and limited strenuous activity during peak afternoon hours.
• A sharp cooldown arrives Wednesday with highs dropping roughly 20 degrees and a slight chance of showers or isolated thunderstorms, with erratic overnight gusts possible before milder conditions return Thursday and a potential brief warmup Friday.