Widespread U.S. Heat Wave Brings Dangerous Conditions

A significant heat wave is striking a large portion of the United States this week. The National Weather Service has reported elevated temperatures that are expected to rise even higher due to intense humidity, especially as the July Fourth holiday approaches.

The heat wave will affect regions across the lower Great Lakes, the mid-Atlantic, and the valleys of the Mississippi and Ohio Rivers. Cities such as New York, Philadelphia, Washington, Baltimore, Chicago, St. Louis, and Detroit will experience some of the highest temperatures recorded this year as they host World Cup matches. Southern cities, including Dallas, Little Rock, and Memphis, will also experience severe heat conditions.

These high temperatures are anticipated to continue into the following weekend across the Great Plains, southeast, and mid-Atlantic regions. According to forecasters, this marks the summer’s first extensive heat wave, impacting a significant portion of the country. While the Four Corners area faces dangerous fire weather conditions, the central and eastern U.S. sees expanding heat. Severe thunderstorms persist across the northern Plains and Upper Midwest, with flood warnings extending from the Rockies to the Mid-Atlantic.

The temperature range is expected to reach the 90s to low 100s Fahrenheit (mid to high 30s Celsius). The humidity will push heat indices to 100-110 degrees Fahrenheit (40-43 Celsius), and potentially as high as 115 Fahrenheit (46 Celsius). Even at night, temperatures will remain in the 70s Fahrenheit (21-26 Celsius), offering little respite.

A National Weather Service heat index map released on June 28, 2026, highlights the dangerous heat conditions expanding across the eastern two-thirds of the United States. The heat index considers humidity to provide an accurate sense of the real feel temperature, advising on the dangers of prolonged exposure or strenuous activity.

Regions like Phoenix, Las Vegas, central Texas, and much of the southwest have already experienced temperatures near 100 Fahrenheit. During extreme heat events, the National Weather Service urges the public to limit outdoor activities, maintain hydration, and ensure access to air-conditioned areas.

The Centers for Disease Control and Prevention warns that high temperatures can affect everyone. Symptoms of overheating include muscle cramps, dizziness, heavy sweating, shortness of breath, headaches, weakness, and nausea.

While parts of the U.S. experience severe heat, much of the western regions remain significantly cooler, with temperatures 20 to 35 degrees below average in areas like the Northwest and northern Rockies.

Meanwhile, Europe is also facing a heat wave. On Saturday, Germany recorded a high of 106 degrees Fahrenheit, with Switzerland, the Czech Republic, Denmark, and France similarly experiencing elevated temperatures. In France, numerous drowning incidents occurred as people sought relief from the heat by swimming.