Overview
- National Weather Service offices issued and repeatedly extended Extreme Heat Warnings across Southern California, the Desert Southwest and parts of Arizona during late August because daytime highs topped 103–115°F and many sites recorded unusually warm overnight lows.
- The regionwide warnings that ran through Saturday are expiring and a cooling trend began Sunday, with forecasts calling for highs to fall toward or below seasonal averages by midweek.
- Forecasters are monitoring Tropical Storm Karina and a weak northern Gulf low for the midweek period because they could raise high cloud cover, boost humidity and produce a small (roughly 15–30%) chance of light rain in parts of Southern California.
- Local officials kept heat‑safety measures in place through the weekend, operated public cooling centers, urged hydration and limits on outdoor work, and warned that coastal and mountain gap winds could gust into the 40–50 mph range causing blown debris and isolated power outages.
- Unusually warm coastal water off San Diego — sea bottom temperatures near 76.6°F at Scripps Pier — and a run of warm nights that reduced physiological relief increased cumulative health risk and are reasons public agencies urged continued vigilance even as temperatures ease.