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.

At least 34 people have died in the US after violent tornadoes tore through several south-eastern states, flipping cars and flattening homes. In Kansas, a dust storm on Friday afternoon caused a crash with more than 50 vehicles, killing at least 8 people. Texas saw a similar mass pile-up.

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