A Dangerous Heat Dome Bakes Much of the U.S. for the Fourth as the West Stays Mild

Much of the United States will spend the Fourth of July under a punishing heat dome — a dome of high pressure that parks hot air over a region and lets it build day after day — while the West Coast, including Southern California, largely sits it out.

Where the heat is

Forecasters describe a heat dome settling over the central and eastern parts of the country, with dangerous conditions from the Plains through the Midwest, the Mississippi and Ohio valleys, the mid-Atlantic and the Northeast, NPR reported. The National Weather Service has posted extreme-heat warnings, watches and advisories across dozens of states, with heat-index values — how hot it feels once humidity is factored in — forecast to climb well into the triple digits in many cities. Just as dangerous, forecasters note, are the nights: in some areas temperatures are expected to stay in the 80s after dark, giving bodies little chance to recover. Hundreds of daily temperature records could fall over the holiday weekend, CBS News reported.

Why it's dangerous

Heat is the deadliest form of extreme weather in the United States in a typical year, and older adults are especially at risk. The stretch of relentless daytime heat with little overnight relief is the kind that sends people to emergency rooms and strains power grids as air-conditioning demand spikes. Authorities' advice is consistent: drink water, limit strenuous activity during the hottest hours, never leave children or pets in cars, use cooling centers if you lack air-conditioning, and check on elderly neighbors and relatives, per FEMA's guidance.

The view from Southern California

For Angelenos, the timing is fortunate. The heat dome is centered far to the east, and Southern California is forecast to stay comparatively mild over the holiday — closer to the 70s along the coast, according to local forecasts — a striking contrast with the swelter gripping the rest of the country. Interior valleys and deserts are always warmer, and conditions can change, so officials still advise knowing where cooling centers are. But for most of the region, this Fourth of July looks like one to enjoy outdoors rather than endure indoors — a reversal from many recent summers when the West baked and the story was here at home.