Question for alarmists: Before the Depression, why were summers so hot in Washington, DC?

Inauguration Weather: Swearing-In Date Switcheroo - Capital Weather Gang

...[Sen. George Norris] also took climatology into account. Here's what he said in a 1924 House hearing:

The thing I am anxious to do is to get the Congress to working in January, as soon as possible, because we all recognize that the best time for Congress to work and the time it can do the best work, is before the hot weather of August and July comes on in Washington, and the longer we put it off the more liable we are to push Congress over into the summer months of Washington which is an undesirable thing, as we all know. [Keep in mind that air conditioning didn't reach the Capitol building till the 1950s.]

Another idea was to keep the inaugural date as March 4 and have the new Congress meet right away. But this would likely push sessions into the summer, and that didn't sit well with Norris or with Rep. Charles Gifford (R-Mass.), who said:

It would be a serious thing to my mind to leave Congress in session here in the summer and make it a yearly occurrence. It would make it almost unbearable. We would not do good work.