In Oklahoma, witnesses have been describing heavy rain, hail and storms that seemed to rock the walls yesterday.
Officials are investigating whether tornadoes are to blame. The storms were severe enough to topple trees and knock out power to thousands of residents. One tree fell onto a gas meter, which spewed gas into the air and forced the temporary evacuation of about 50 people who lived nearby.
Meteorologists are checking reports that two tornadoes were spotted last night. Oklahoma state officials say there were no reports of major injuries or damage.
Highway motorists also spotted the possible tornadoes in Oklahoma City during rush hour.
As a National Weather Service spokesman puts it, "it's that time of year."