It's going to be a hot July Fourth for much of the country

People cool off at the fountain in Millennium Park in Chicago as temperatures topped 90 degrees on Monday. Forecasts predict extreme heat this week across the Midwest and East Coast. Scott Olson/Getty Images hide caption toggle caption Scott Olson/Getty Images A heat wave centered on the Midwest and parts of the East will break temperature records in some places in the coming days as the thermometer pegs out as high as 105 degrees in some places moving toward the July Fourth weekend, forecasters say. As of Tuesday morning, the National Weather Service (NWS) estimates that the extreme heat warnings affect more than 102 million people nationwide, with another 43 million under extreme heat watches. Geographically, the area includes a broad swath of the Midwest, Ohio Valley and Northeast, including Illinois, Indiana, Ohio, Missouri, Iowa, Wisconsin, Michigan, Kentucky, parts of Minnesota, Kansas, Tennessee and Pennsylvania. New Jersey, southern New England, downstate New York (including New York City), and potentially the Washington, D.C.–Baltimore area are also affected, according to the NWS. The extreme temperatures are being caused by a heat dome – an area of high pressure that acts like a lid, trapping hot air. "We're looking at temperatures generally 100 to 105" for Thursday and Friday, as the heat wave peaks, according to NWS meteorologist Joe Wegman. He says the mid-Atlantic will experience temperatures 10 degrees to 15 degrees above normal. "On the East Coast, for sure. …