President Obama has declared a major disaster in the state of Oklahoma after a tornado flattened homes and schools.
It's estimated that around 24 people have died in the storm.
Worst hit was the town of Moore which is south of Oklahoma city.
Tornadoes are common in this area of America but this one was particularly strong with winds of 200mph (320km/h).
About 250 people are being treated in hospitals and some are still missing.
Watch Ricky's report.