More than 185 million people across the eastern half of the United States are under warnings as a severe heatwave brings dangerous temperatures and humidity. The heat index, which measures how hot it feels when humidity is factored in, could reach 120F (49C) in parts of Mississippi and Louisiana.
The south-east is bearing the brunt of the extreme conditions, with heat index values forecast between 105F and 113F (40.5C to 45C) from the Carolinas through Florida. Cities including Des Moines, St Louis, Memphis, New Orleans, Jacksonville and Raleigh are under extreme heat warnings, with temperatures climbing into the mid-90s and low 100s Fahrenheit.
Level 4 heat risk—the highest category—covers much of Florida and extends into Georgia and the Carolinas. Tampa reached 100F (37.8C) on Sunday, an unprecedented milestone. Other cities have broken daily temperature records, with more expected to follow.
The heat and humidity are expected to persist through midweek, with overnight temperatures only dipping into the 70s Fahrenheit, offering little relief. A cold front later in the week is forecast to bring a drop in temperatures across the eastern US by the weekend.
According to the Environmental Protection Agency, extreme heat causes more than 1,300 deaths per year in the US. The National Oceanic and Atmospheric Administration (Noaa) notes that excessive heat is already the leading cause of weather-related deaths, and the problem is intensifying. However, federal agencies like Noaa are operating at reduced capacity due to staffing cuts, with hundreds of meteorologists having left the National Weather Service in recent months.
