New rounds of severe thunderstorms are underway and life-threatening, potentially catastrophic flooding risks are brewing in the central and eastern United States Tuesday, putting more than 50 million people at risk of dangerous weather this week.

At least one person has died in southwest Oklahoma after flash flooding hit the region, with authorities warning people to stay off the roads as severe weather warnings continue.

Two people died Saturday night in an Oklahoma City suburb after floodwaters swept their truck into a creek, police said. One of the deceased was 12 years old.