ATLANTA — More than 15 million people from Texas to Florida were under threat of severe storms and the potential for more tornadoes Monday, many of them in areas previously hit during one of the most active periods for twisters on record.

At highest risk for severe storms and tornadoes was a zone stretching from southeast Texas through much of Louisiana and the Gulf Coast regions of Mississippi and Alabama, to the Florida Panhandle, according to the national Storm Prediction Center. Some of the worst weather around midday Monday was in the Florida Panhandle, where residents were under a tornado warning in parts of Okaloosa and Santa Rosa counties.

Monday’s storms come shortly after one of the most active periods of severe weather in U.S. history, from April 25 through May 10, the National Weather Service said in a recent report. At least 267 tornadoes were confirmed by the weather service during that time, the agency said.

Among the many tornadoes: a pair of twisters that caused heavy damage Friday in Florida’s capital, Tallahassee. As the two tornadoes crossed the city from east to west, they damaged homes and businesses, caused a construction crane to collapse, and severely damaged the outfield fence at a baseball stadium at Florida State University, the weather service said.

Severe thunderstorms and flash flooding were predicted for portions of the Gulf Coast Monday and the Southeast Tuesday, according to the National Weather Service. Alabama received 6.04 inches of rain in April, compared to an annual April average of 4.86 inches.