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" refers to the process known as evapotranspiration. Corn plants, like other plants, absorb water through their roots to be used for growth and photosynthesis. Any excess moisture is then released as vapor via tiny pores in their leaves called stomata into the atmosphere, according to crop intelligence firm Taranis.

The combination of corn sweat, the exhalation of water vapor through leaves, and a heat dome is bringing dangerously hot conditions to millions of people.