President Donald Trump has activated the National Guard in tornado-struck Arkansas after storms ripped through multiple states over the weekend, leaving at least 37 dead.

Thousands of power outages were reported Saturday as a deadly severe weather outbreak moved across the Midwest and South.

The most fatalities were in Missouri. Forecasters warned that tornadoes, hail and violent winds continue to threaten states in the Deep South, from Louisiana to Georgia.

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.

A deadly tornado outbreak ripped through the Midwest and South over the weekend, leaving destruction, power outages and tragic loss in its wake.

A deadly tornado outbreak ripped through Missouri, Illinois, Arkansas and Mississippi overnight Friday, leaving destruction, power outages and tragic loss in its wake.

Numerous significant tornadoes are expected Saturday afternoon and evening, with the highest risk across several states in the Deep South, forecasters say.

Tornadoes in the South and Midwest overnight and early Saturday left 11 dead in Missouri. More tornadoes are forecast Saturday and Sunday.

The weather cut a swathe of destruction across an area of the country that is home to more than 100 million people.