Why ‘corn sweat’ will make this week’s heat wave even worse

This Midwestern phenomenon could increase humidity levels in already-sweltering states—from Ohio to Illinois—through Thursday.

Another crushing heat wave is hitting the United States this week. The so-called “dog days of summer” are in full swing for much of the eastern two-thirds of the U.S., as a heat dome over the Mississippi River and Ohio River valleys gradually builds later in the week, according to the Weather Prediction Center (WPC) at the National Oceanic and Atmospheric Administration (NOAA).