Climate change intensifies midsummer U.S. heatwave for millions

July 21, 2025

A prolonged stretch of unusually hot, midsummer heat and humidity will grip a large portion of the United States from July 21 to 25. What began across the Southeast over the weekend is forecast to expand into the mid-South early in the week, then expand into the Midwest by mid-to-late week. 

A Climate Central analysis finds that human-caused climate change made this excessive heat at least three times more likely for nearly 160 million people, nearly half of the U.S. population.

Note: This event may continue beyond July 25. Use the Global Climate Shift Index map to stay updated on heat in your region.

How unusual is the forecasted heat?

• Triple-digit highs are forecast for multiple days in parts of Arkansas, Kansas, Missouri, northern Louisiana, Oklahoma, and Texas. 

  • Forecast highs in the mid-to-upper 90s spread into the lower Midwest by midweek, with similar temperatures possible in the Northeast by late week.

• High humidity will intensify the heat, especially in the Central Plains, Midwest, and Mississippi and Ohio valleys, where heat index values could reach between 105°F to 110°F.

• Unusually warm overnight lows in the mid-70s to low 80s — as much as 5°F to 15°F above average for this time of the year — are forecast to potentially break record high minimums (the warmest low temperatures on record) in states like Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Missouri, South Carolina, and Tennessee.

• A strong area of high pressure, known as a heat dome, will anchor this weather pattern, funneling hot, humid air north and northeast throughout the week.

How has climate change influenced this heat?

• Climate Shift Index (CSI) levels of 5 — the highest possible — are forecast across wide swaths of the country, from Salt Lake City and Santa Fe to Tallahassee and Montgomery, meaning human-caused climate change made this extreme heat at least five times more likely. This signals an exceptional climate-influenced event.

• Over the full period, nearly 160 million people across the interior United States  — nearly half of the population — will experience at least one day with a CSI of 3 or higher, indicating a strong influence from climate change.

What do experts say?

Dr. Kristina Dahl, VP of Science at Climate Central, said: 
“This is not your grandmother’s heat wave. Yes, July is usually a hot month, but climate change is making this heat wave significantly hotter — and therefore more dangerous — than heat waves of the past.”

To request an interview with a Climate Central scientist, please contact Abbie Veitch at aveitch@climatecentral.org. 

How do we know climate change is influencing this heat?

The Climate Shift Index uses peer-reviewed methodology and real-time data to estimate how climate change has increased the likelihood of a particular daily temperature.

Reporting resources

• For quick facts about extreme heat in the U.S. → Extreme Heat Toolkit

• For accessing this data in MAX or Baron Weather Systems → Climate Shift Index in KML

• For an in-depth guide about how to report on attribution science and extreme weather types → World Weather Attribution’s reporting guide 

• For the latest research-backed messaging to use while reporting on climate change → Potential Energy’s Guide to Reporting on Unnatural Disasters