U.S. Experiences Worst Day of Historic Heat Wave

Nueva Voz · IA

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The United States is experiencing its worst day of the heat wave on Wednesday with more than 113 million people at major or extreme risk. According to information from the National Weather Service, the northern and northeastern parts of the country face dangerous temperature and humidity conditions. The meteorological authority warned in its latest bulletin of anomalous heat and humidity in the northern and midwest U.S. that will extend toward the northeast in the coming days and bring temperatures between 32 and 38 degrees Celsius. This situation represents the worst day of a heat wave that began the weekend of July 4.

Additionally, the National Weather Service issued a major heat alert on Wednesday affecting 113.8 million people residing across a wide swath of territory from the Dakotas to Virginia. Including major cities such as Chicago and New York, isolated areas of California and Florida are also affected. This alert warns of potential risks for people lacking adequate cooling or hydration, as well as impacts on healthcare systems and industries. The NWS website details that nearly two million people in the Dakotas are living under an extreme alert on this day.

Which regions are most affected by extreme heat?

The 113.8 million people under major heat alert reside across a wide swath of territory from the Dakotas to Virginia. According to NWS information, the most affected major cities include Chicago with its metropolitan area of millions of residents. New York also faces extreme conditions that have activated municipal emergency plans to protect vulnerable residents. Isolated areas of California and Florida add millions more to the total number of people at risk.

U.S. Experiences Worst Day of Historic Heat Wave — People cool off during the heat wave in Washington (U.S.), July 4, 2026. EFE/Graeme Sloan

Nearly two million people in the Dakotas are living under an extreme alert on this day that extends danger to infrastructure and through the night. This alert level indicates serious risks for public health and essential systems. Nighttime temperatures remain dangerously high, preventing adequate bodily recovery. Elderly people and young children face greater vulnerability during these prolonged extreme conditions.

The agency forecasts that heat conditions will depart the most populated areas beginning Thursday. According to NWS information, that day both alerts will affect 95 million residents instead of the current 113 million. That number will decrease to 66 million on Friday and 33 million on Saturday, primarily in the southeastern part of the country. The heat wave in the U.S. will gradually diminish in scope over the next four days.

What are the risks to public health?

This alert warns of potential risks for people who lack adequate cooling or hydration during the heat wave. According to NWS information, healthcare systems face additional pressure from increased heat-related emergencies. Industries also report impacts on operations.

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