Vast swathes of the central and southern United States remain gripped by an intense heatwave, with extreme heat warnings affecting at least 40 million people across a broad region stretching from California to Mississippi. Temperatures have been described as 'extraordinarily hot', with heat indexes consistently exceeding 38 degrees Celsius (100 degrees Fahrenheit) for a second consecutive day, according to the National Weather Service (NWS).
The sweltering conditions are the result of a 'heat dome' – a meteorological phenomenon where atmospheric conditions trap heat, intensifying and prolonging already high temperatures. This has led to exceptionally humid air, making outdoor conditions particularly challenging. Pete Miller, an outreach manager for Threshold CoC, a homeless services network in Omaha, Nebraska, highlighted the severity, stating, "We’re seeing a lot of people who are exhausted, drained by the heat in a way that is really dangerous." He added, "The humidity is insane. You stand outside for 30 seconds and you get drenched. And it’s going to be like that all night.”
Record-breaking temperatures have been observed, including an all-time high of 44.4 degrees Celsius (112 degrees Fahrenheit) reported in Rapid City, South Dakota, on Saturday. The extreme conditions led to the cancellation of a planned horse race in Shakopee, Minnesota, on Sunday. While the core of the heat is expected to shift southward by early next week, bringing some temporary relief to the central US by the middle of the week, meteorologists warn that high temperatures could return by the weekend.
Beyond the direct heat, the moist air around the periphery of the heat dome is also contributing to other volatile weather patterns. On Sunday, areas around the Great Lakes faced risks of severe thunderstorms, flash flooding, and hail, with the potential for heavy storms anticipated to move eastward in the coming days. NWS meteorologist Bob Oravec explained the interconnectedness, stating, "If you have a heat dome in one part of the country, you’ll have a different corresponding weather in another part. It’s all related.”
Authorities are issuing strong warnings, particularly for children, older adults, and individuals with pre-existing medical conditions, who are at heightened risk of serious health complications, including heat stroke and even fatalities. Experts advise seeking air-conditioned environments or cooling centres, maintaining adequate hydration, and limiting direct sun exposure. This ongoing heatwave underscores a broader trend, with the continental US having experienced its second-hottest first half of the year on record in 2026, according to the National Centers for Environmental Information, a situation exacerbated by the climate crisis.