By Holly Yan and Monica Garrett, CNN
CNN — Many of these places can't absorb any more rain, but Mother Nature doesn't care.
From Texas to the Carolinas, more than 21 million people are under a flood watch or warning Tuesday, CNN meteorologist Dave Hennen said.
"More heavy rain is expected over the Southeast, where rainfall totals over the last 30 days are as much as 200-300% (above) normal," Hennen said.
"Several more rounds of heavy rain and storms are forecast as the next system pulls out of the Southwest."
That's especially bad because the ground is already saturated, meaning it can't soak up more rain -- making flooding much more likely.
And flooded roads contribute to many weather-related deaths, as drivers attempting to cross a flooded road get stuck or washed away.
"DO NOT DRIVE THROUGH FLOODED ROADS!! It doesn't matter if the person in front of you did it, or if you don't want to turn around, or it's just easier to go through," the National Weather Service's Birmingham office tweeted. "TURN AROUND AND FIND ANOTHER WAY!"
But flooding isn't the only danger in the Southeast this week.
"Severe storms will also continue in the Southeast, with the threat for tornadoes continuing" Wednesday, Hennen said.
