A severe heatwave has disrupted Fourth of July celebrations across several parts of the United States, with temperatures forecasted to remain above 38°C (100°F) for several days. In Washington D.C., the Great American State Fair, marking the country's 250th anniversary, was temporarily closed after multiple cases of heat-related illnesses were reported. Additionally, a parade scheduled for the holiday in Philadelphia was cancelled due to dangerous heat conditions. The National Weather Service reported that over 165 million people are experiencing record temperatures along the East Coast and Midwest, with Philadelphia and Washington D.C. expected to reach close to their all-time highs of 104°F (40°C) and 103°F with humidity, respectively. The heatwave is causing concern for public safety during the holiday weekend, as US President Donald Trump hosts a celebration marking America's 250th birthday and multiple World Cup matches take place outdoors. Organizers of events have been forced to cancel due to the blistering heat, from New Jersey, Pennsylvania, and Maryland to as far west as Colorado. The intense heat also led to the closure of the fair on the National Mall for several hours on Friday, but reopened later in the day after conditions improved. The DC Fire and EMS Department treated several people for heat-related illnesses at the fair on Friday, with at least 11 people being taken by ambulance from the event. The extreme heat is expected to continue through the weekend, with Philadelphia and Washington D.C. forecasted to remain dangerously hot for those attending outdoor events. Additionally, severe thunderstorms are expected in the northern plains, Midwest, and across to the Great Lakes, bringing a dramatic end to the heat with damaging hail, destructive winds, flash flooding, and even a few tornadoes. The heat is predicted to intensify in Virginia, the Carolinas, and the southeast by Sunday before building in western parts of the U.S. and Canada into next week. Residents are advised to take precautions if planning outdoor activities during this time.