U.S. Public Safety and Infrastructure

A sprawling heat dome that has already shattered March temperature records in at least 14 states is pushing east and could become one of the most expansive U.S. heat waves on record, according to National Weather Service forecasters and weather historians. The high‑pressure system, acting like a "pot lid" trapping hot air, has driven temperatures to 112°F in four locations in Arizona and California, breaking the previous all‑time March record for the Lower 48 by 4°F and coming within 1°F of the hottest April day ever recorded. Meteorologists say Flagstaff, Arizona, is on track for 11 or 12 straight days above its prior March record, while by midweek large parts of the southern and central Plains are expected to see 90s, with roughly one‑quarter to one‑third of the contiguous U.S. "flirting with records" for this time of year. The National Centers for Environmental Information report at least 479 March temperature records broken at official stations between Wednesday and Saturday, and independent climatologist Maximiliano Herrera says the true total is likely higher and includes unprecedented March readings in Mexico that even surpass some historic May or June highs. Experts note that while this event may be less deadly than summer heat waves because humidity is lower and it is not mid‑summer, its sheer geographic scale, timing and intensity are consistent with scientists’ warnings about more frequent, widespread extremes in a warming climate, raising concerns about early-season stress on power grids, agriculture and water supplies.