The frost may harm temperature-sensitive plants typically grown during late spring and summer.
Downpours caused more evacuations in areas where the water had been receding.
The mayor of Cairo, Ill., said the well-being of his 2,800 residents outweighs farmland that would be swallowed up by the rush of water.
As many as a million homes and businesses in Alabama were without power, and Alabama Gov. Robert Bentley said 2,000 National Guard troops had been activated to help.
At least 280 people have been reported dead following a storm system that spawned dozens of tornadoes in the Southern United States on Wednesday.
The death toll from the wave of severe storms and tornadoes in the southern United States on Wednesday has risen to over 200. On Thursday, Alabama residents returned to their homes to survey the damage.
The storms Wednesday spawned tornadoes and winds in five Southern states: Alabama, Virginia, Tennessee, Mississippi, and Georgia. All five states have reported fatalities; 128 have been confirmed dead in Alabama.
Relentless rain over the past several days has residents rushing to prevent floodwaters from invading their communities.
Although Missouri has no death toll from the recent storms and tornadoes ravaging parts of the Midwest, others have not been as lucky.
After days of rain, parts of Poplar Bluff have been submerged. One of the levees has been breached by the Black River, and some residents are evacuating their homes. The Red Cross has set up a shelter at the Black River Coliseum.
Floodwaters are rising all over the Midwest. Popular Bluff is an area of great concern with 1,000 residents already evacuated and more expected by Tuesday afternoon.
Tornado sirens are set up to sound for any threat in Boone County. This policy is based on the unpredictable nature of tornadoes.
The National Weather Service has compiled maps, photos and updated information about the Good Friday tornado.
Damage occurred at Lambert-St. Louis International Airport and at several communities around the airport, including: Bridgeton, St. Ann, Ferguson and Florissant.
The strong storm lifted the roof off Concourse C at Lambert-St. Louis International Airport, causing plate glass to shatter and fly everywhere.
An apparent tornado caused damage at Lambert Airport, and other possible tornadoes were reported at several towns near the airport, including: Maryland Heights, Bridgeton, St. Ann, Ferguson and Florissant.
Three tornadoes reportedly touched down in northeast Missouri. High winds were reported in southeast Missouri. More severe weather is expected later this week.
The river is expected to reach near flood stage by early next week in towns such as Canton, Hannibal, Louisiana, Clarksville and Winfield.
Thunderstorms could bring tornado warnings, hail and strong wind, the National Weather Service said.
The National Weather Service is predicting a wide range of severe weather for Tuesday.