Extreme heat will also scorch much of Texas, where the National Weather Service warned that "many will not be acclimated to this type of heat so early within the year and thus the risk for heat-related illness is higher than normal. Please practice heat safety!"

"It will feel hot and dry initially before eventually becoming muggy and possibly even downright oppressive across the area," read a forecast discussion from the weather service. "Multiple records in jeopardy of being broken," it added.

An early-season heat wave is set to bake huge swaths of the country this week, with record or near-record high temperatures expected across the Plains, the Southwest and much of central and southern Texas.