Record-breaking heat wave hits southern US, affecting millions.

More than 40 million Americans are under heat alerts as high temperatures continue for Texas, Louisiana, Mississippi, and Florida. A severe weather outbreak is stretching from the Plains to the South, with over 1,000 severe storm reports since Tuesday. The combination of heat and oppressive humidity will lead to heat index values of 110 degrees to 120 degrees on Saturday afternoon. Damaging winds and large hail are the main threats for most of the area, but there is a risk for powerful tornadoes around Oklahoma.