Heat warnings cover more than 100 million people ahead of July Fourth

The National Weather Service has issued extreme heat warnings affecting more than 102 million people and extreme heat watches covering another 43 million as a heat wave builds across the Midwest, Ohio Valley and Northeast. The affected region includes Illinois, Indiana, Ohio, Missouri, Iowa, Wisconsin, Michigan, Kentucky and parts of Minnesota, Kansas, Tennessee and Pennsylvania, along with the Baltimore area.

A heat dome of high pressure is trapping hot air over the region. National Weather Service meteorologist Joe Wegman said temperatures will generally reach 100 to 105 degrees on Thursday and Friday.

outlook Wegman said the mid-Atlantic will see temperatures 10 to 15 degrees above normal and that record-breaking readings are expected on the East Coast. Humidity will push heat indices to 105-115 degrees through Thursday in parts of the Midwest and Mississippi Valley, then shift to the Mid-Atlantic and Ohio Valley in following days.

Overnight lows remaining in the 70s will limit relief, increasing the risk of heat-related illness for vulnerable populations and those without adequate cooling.

Safety measures and cancellations Wegman said the heat threatens older people, those with respiratory problems and pets, but affects people of all ages and health conditions. Temperatures are forecast to ease slightly on Saturday. Officials recommend staying indoors when possible, staying hydrated and taking frequent breaks from exertion.

The heat wave has already prompted cancellations of summer camps and other outdoor activities in the Midwest, according to The Associated Press. Communities have opened cooling centers and urged residents to limit outdoor time.