Heat dome expands east, putting millions under dangerous alerts

The heat dome that has scorched the West is pushing east, and a significant heat wave is underway across the Intermountain West, Northern Plains and Upper Great Lakes. Millions of Americans are under heat alerts as the extreme temperatures spread from the Midwest to the East Coast.

The National Weather Service issues heat advisories and excessive heat warnings based on local heat-index thresholds, with advisories generally marking dangerous heat and excessive heat warnings signaling conditions that pose a significant threat to life. The agency also tailors alerts by local forecast office because communities acclimate differently to heat. On Monday, July 13, 2026, NWS Mount Holly issued an Extreme Heat Watch for parts of New Jersey, including Somerset, Middlesex, Western Monmouth, Ocean and Southeastern Burlington counties, from Wednesday morning through Wednesday evening.

The western side of the system has already produced severe conditions before the heat shifts farther east. On July 9, 2026, some desert areas in the West could reach 117 degrees. The heat wave is peaking in intensity through midweek and will linger across parts of the Northern Plains and Midwest until this weekend.

In 2025, a heat dome trapped more than 90 million Americans in extreme temperatures, with National Weather Service alerts stretching from Nebraska to Florida. The current dome is covering a wide national corridor, with the West baking first and the East now moving into the same dangerous setup as humidity makes the air feel even hotter.