Millions of Americans across the country are on alert for a severe weather outbreak as violent, long-track tornadoes with damaging winds of up to 80 mph and large hail are expected across the Midwest and South with the cross-country storm moving east.

Meanwhile, the severe weather threat will linger through Sunday from Florida northward into the upper Ohio River Valley, forecasters warned.

A new Tornado Warning has been issued for parts of the San Joaquin Valley early Monday evening as severe weather continues to move through the area.

Heather Waldman explains a tornado warning from 3 p.m. to 3:30 p.m. on March 17. The warning covered parts of Tuolumne, Mariposa and Merced counties and has since expired.

Tornado warnings issued for parts of Mariposa, Tuolumne and Merced counties on Monday afternoon have expired, according to the National Weather Service.

The deadliest tornado in recorded U.S. history occurred 100 years ago. The Tri-State Tornado touched down in southeastern Missouri on March 18, 1925.

Portions of West Virginia, Ohio and Pennsylvania were under a new tornado watch issued on Sunday by the National Weather Service, as the death toll from storms rose to at least 34 people in six states since Friday.