Unforgiving heat wave forecast in swaths of U.S. in the coming days

An unforgiving heat wave is gripping much of the Lower 48, bringing triple-digit temperatures to the nation’s three most populous states — California, Texas and Florida — and is poised to set a litany of records.

In the Southwest, readings are expected to climb as high as 130 degrees, while the southern Plains and Southeast will face an oppressive overlap between extreme temperatures and tropical humidity.