U.S. heat wave triggers record temperatures and widespread alerts

A massive heat dome is sweeping the United States, driving record‑breaking temperatures and dangerous humidity from the West to the East. More than 40 million people are under heat alerts, with the National Weather Service warning of heat‑index values that could reach 115 °F in parts of the Northeast. Record highs were set in Salt Lake City (≈43 °C/109 °F) and Billings, Montana (≈44 °C/111 °F), while other western cities topped 100 °F.

Extreme‑heat warnings now cover 23 states, affecting power demand, outdoor events and causing a surge in heat‑related emergency visits. Nighttime temperatures are expected to stay above normal, with over 90 temperature records slated to be tied or broken this week, many of them overnight highs. The prolonged heat also fuels wildfire risk in the Southwest, where dry fuels and gusty winds have already led to large fires in Utah and Arizona.

Health officials stress that vulnerable groups—such as the elderly, children, pregnant people, outdoor workers and those without air‑conditioning—face heightened danger. Authorities across the country have issued advisories, opened cooling centers, and urged residents to stay hydrated, limit strenuous activity, and check on neighbors.