WATCH: Lightning strike in South Carolina injures 20 as heat wave scorches East Coast

More than 120 million Americans remain under heat alerts Wednesday as record-breaking temperatures and dangerous humidity grip the East Coast.

​More than 120 million Americans remain under heat alerts Wednesday as record-breaking temperatures and dangerous humidity grip the East Coast.   More than 120 million Americans remain under heat alerts Wednesday as record-breaking temperatures and dangerous humidity grip the East Coast.