Major U.S. Heatwave to Last Through July Fourth

A prolonged and significant heat wave is set to impact much of the United States from the official start of summer through the Fourth of July, with about 170 million people affected. Extreme heat and humidity are forecast across the Midwest, South, East Coast, Southeast, and Mid-Atlantic, with cities such as Chicago, Detroit, St. Louis, and the D.C. area expecting temperatures in the 90s for several days. New England, including Boston and Vermont, will also face a sharp increase in temperatures and humidity, with heat index values exceeding 100°F in some areas. Afternoon showers and thunderstorms, some severe, are likely in the affected regions. The weather pattern is driven by a dome of high pressure and unusually warm ocean waters. Forecasters urge residents to prepare for extended periods of hot, muggy conditions.