A phenomenon called "corn sweat" could exacerbate the impacts of the extreme heat blanketing a large portion of the U.S., according to experts.

Corn sweat, a Midwestern phenomenon, could increase humidity levels in already-sweltering states—from Ohio to Illinois—through Thursday.

Every summer in the Midwest, residents brace themselves for not only sweltering temperatures but something a bit more mysterious – a stifling heat that seemingly sticks to the skin.