Overview
- National Weather Service products place about 47 million people under extreme heat warnings and roughly 56 million under heat watches as the heat dome expands eastward.
- Forecasters forecast daytime highs in the 90s to low 100s with humidity inflating feels‑like values toward 105–110°F, and limited overnight cooling that will keep lows in the mid‑ to upper‑70s.
- Local officials have already canceled or modified outdoor events, opened cooling centers, and urged hydration and reduced exertion for vulnerable people including older adults, children, outdoor workers, and those without reliable air conditioning.
- Isolated to scattered thunderstorms may appear along the heat‑dome edges or sea breezes and could briefly cool some areas while also producing gusty winds, heavy downpours, or hail that complicate responses.
- Meteorologists warn the highest risk comes midweek through the July 4 weekend, with record‑threat potential in some metro areas and continued updates possible as frontal passages or storms shift timing and intensity.