Dangerous heat dome to bake much of the U.S. this week

NOAA’s Climate Prediction Center forecasts dangerous heat will not break quickly, with extreme temperatures likely to continue into July 6-12 across much of the central and eastern contiguous United States. The forecast calls for heat index values above 100 to 105 degrees in many places, and warm nights that will limit the overnight cooling people usually rely on to recover.

The CPC has placed the eastern Central and Southern Plains, the Central and Lower Mississippi Valley, the Southeast Atlantic states and the Mid-Atlantic under a moderate risk of extreme heat for Monday, July 6. Much of the central and eastern U.S. faces at least a slight risk from July 6-8.

NOAA’s National Weather Service HeatRisk guidance, updated June 28, classifies magenta-level heat as rare or long-duration extreme heat with no overnight relief. The category flags danger for people without cooling or hydration, as well as health systems, industries and infrastructure that come under stress when hot days stack up and nights stay warm. The threat is especially sharp when humidity drives the heat index higher than the thermometer reading.

AccuWeather projects the core of the heat dome over the Ohio Valley, middle Mississippi Valley and Tennessee Valley. In that setup, Chicago could see at least five straight days with highs of 90 degrees or more next week, while St. Louis may log eight consecutive days at or above 90. Chad Merrill, an AccuWeather senior meteorologist, expects conditions to turn very hot and humid in the East for the second half of next week, with multiple days in the 90s likely along the Interstate 95 corridor.

The National Weather Service expects the humidity to make temperatures feel hotter, with several days of high heat settling in across the lower Great Lakes, Mid-Atlantic and the Mississippi and Ohio River valleys.