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I spent July 4 at the ballpark, for a game between the Washington Nationals and the Boston Red Sox. The stadium was supposed to be filled to capacity. But by the game’s middle innings, a huge number of seats — about half, in some sections — were empty, even though the game was tied. In more than 40 years of attending ballgames, I had never seen anything quite like it.

What was going on? It was a brutally hot day in Washington, and many people found it too uncomfortable to remain in their seats. So they decided to escape the sun and wander the stadium’s shaded concourses or to leave the ballpark altogether.

Washington is often hot in the summer, of course, but the heat wave of the past week has been decidedly abnormal. “For the week through Tuesday, 227 U.S. records were broken for highest temperature for particular days, and another 157 were tied, federal statistics show,” Malcolm Ritter of The Associated Press reported. Burlington, Vt., for example, experienced its highest daily low temperature on record: On Monday, the temperature never fell below 80 degrees.