An average of 1,200 tornadoes hit yearly, and the United States will probably get more killer supercells spawning tornadoes and hail as the world warms.

The severe weather stretched from Texas to Ohio, causing tornadoes and flooding across the central United States.

A life-threatening outbreak of long-lived and strong tornadoes is expected today in parts of the central and eastern US from a powerful, wide-reaching spring storm.

The National Weather Service says a "multi-day catastrophic and potentially historic" storm is expected to impact multiple states. Thousands have lost power in Missouri and other states, and a person was killed Wednesday evening in the southeast part of the state.

A powerful F3 tornado touched down in Hanover, Pennsylvania, on April 5, 1952, leaving a 17-mile path of destruction. The tornado, the strongest ever recorded in York County history, caused $2.5 million in damages, equivalent to about $30 million today.

Millions of people are under tornado watches across the central United States on Sunday, as a volatile weather system has triggered power outages and huge hail. Nearly 175 million people from Illinois to eastern Texas and beyond could be affected,

The National Weather Service described the disaster as "a once-in-a-generation to once-in-a-lifetime" event, warning that the worst may still be ahead.