 The U.S. is celebrating the Fourth of July in the nation's capital today with the annual National Independence Day parade on Constitution Avenue. This year's Fourth of July celebrations will have the usual barbecues, fireworks and other outdoor activities, though under a blanket of heat in many parts of the country. According to the National Weather Service, around 134 million people in the U.S. are under some kind of heat alert, with many regions seeing temperatures in the 90s or even the triple digits.