Strong-to-severe thunderstorms are in the forecast for sections of the upper Midwest and Ohio Valley.
Related severe weather hazards include large hail, damaging winds, tornadoes and heavy rain that could bring the risk of flooding.
This region is also experiencing very poor air quality from wildfire smoke pouring in from Canada, which will spread into the Northeast later Wednesday and into Thursday.
Additionally, excessive heat watches and warnings are in place once again for the Southwest, over the southern Plains and across the Gulf Coast states.
Temperatures will soar to record levels with dangerous humidity.
Those susceptible to heat-related illness should take all necessary precautions.