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Heat dome to bake central and eastern US through July 4, putting 200 million at risk

An upper-level high pressure ridge is driving 90-100°F temperatures across more than two dozen states from the Great Lakes to the Gulf Coast, with heat index values reaching 115°F in spots; peak danger is July 3-4 as over 100 million people face Major or Extreme heat risk

天气· active 生活如何改变·什么崩了 ·3 视角 · ·rbtfl 更新 2026年6月29日

Summary

A sprawling upper-level high pressure ridge is driving a heat dome across more than two dozen central and eastern US states, with temperatures forecast to reach the upper 90s to low 100s Fahrenheit and heat index values of 100-115°F in the Great Lakes, mid-Atlantic, Mississippi Valley, and Southeast. Over 100 million people face Major or Extreme heat risk. The event is expected to peak July 3-4, coinciding with the 250th anniversary Fourth of July weekend, and then linger along the I-95 corridor.

Why it matters

Coming on the heels of back-to-back high-temperature summers, the event tests urban heat infrastructure and emergency services at a peak-demand holiday weekend when outdoor gatherings are common. Heat is the leading cause of weather-related death in the US.

What to watch

  • NWS heat alerts and heat emergency declarations by state.
  • Power grid stress in the affected regions (MISO, PJM) as demand spikes.
  • Whether the dome breaks before July 4 or extends into the holiday week.