A slew of weather warnings and watches extended Tuesday from northeastern Texas to southern Maine as a stalled frontal system threatened some areas with heavy snow and others with significant rain.
The National Weather Service said snow is likely in southern New England and the northern Mid-Atlantic states. Flash floods are possible in parts of the Southeast.
Traveling conditions in several states have already become precarious.
More than 170 departing flights from Dallas-Fort Worth International Airport were canceled due to freezing rain at destinations throughout the South.
In Louisiana, police in DeSoto Parish had responded to at least 20 incidents, many on Interstate 49. Lt. Donnie Barber of the sheriff's office said there were no reports of life-threatening injuries.
According to the Louisiana Transportation Department, more than 18 miles of Interstate 220 near Shreveport were closed.
Many bridges in northern Mississippi were iced over, said Brett Carr, a spokesman with that state's emergency management agency.
Carr added that several hundred power customers in Greenville, near the Mississippi River, were in the dark.
Mississippi Gov. Phil Bryant issued a state of emergency "for all counties impacted by the freezing rain, flooding and severe weather."
Tennessee also has issued a state of emergency for areas affected by the weather.
The state's emergency operations center was calling in staff to monitor power outages and assist counties with roadways, said Dean Flener, a spokesman for the Tennessee Emergency Management Agency.
The state of emergency allows local governments to call on aid from the state.
The Tennessee Valley Authority said it was taking the unusual flood-prevention measure of spilling 1.5 million gallons of water per second through the Kentucky Dam near Paducah from the Tennessee River into the Ohio River. The dam usually puts out 400,000 gallons per second, a spokesman said.