When Thomas Jefferson measured the temperature on July 4, 1776, the high was 76 degrees Fahrenheit in Philadelphia.Two hundred and fifty years later, millions of people across the eastern half of the U.S.
were under extreme heat warnings as they celebrated that anniversary.The heat dome that settled over the Midwest and Atlantic coast then gave way to multiple rounds of severe storms and flash flooding, according to the National Weather Service.This extreme weather did not come as a surprise, and many cities across the country were prepared: Independence Day parades in Philadelphia and Washington, D.C., were canceled, while Boston did not open access to its annual fireworks event until 4 p.m.Meanwhile, dozens of heat-related deaths were reported across the country and emergency rooms saw high numbers of people suffering from heat-related illnesses.Extreme heat could be a mark of many Independence Days in the future, experts say.Climate change, caused primarily by burning fossil fuels, is making heat waves hotter and longer.
The average number of heat waves in the U.S.has doubled since the 1980s."It's not an anomaly.
It's a preview," said Michael Rawlins, associate director of the Climate System Research Center at the University of Massachusetts Amherst.On July 4, a large portion of the Eastern U.S., from New York to Georgia, had "extreme" rates of emergency department visits for heat-related illnesses, according to the Centers for Disease Control and Prevention's daily heat-related illness tracker.At least 40 deaths have been reported by local officials in connection with the heat wave: 29 in New Jersey, 3 in New York, 4 in Philadelphia, and 4 in Illinois.However, experts said heat-related deaths are hard to pinpoint.Heat-related deaths are undercounted and often heat exacerbates an underlying medical condition."Teasing out which of the deaths are due to extreme heat and which are due to other causes is not an exact science," said Steven Cohen, who is the direct...