"We're 85 percent underwater," Union County Sheriff Tommy Wilhite said in a mid-afternoon interview. "Some of these places, it's four or five feet deep."
The Tallahatchie River in New Albany rose to more than twice its level. The river is normally at 11 to 12 feet, but by Sunday night, it had risen to more than 25 feet.
The river expected to reach 28 feet this morning, said Jim Branda, a meteorologist with the National Weather Service in Memphis.
The rain, floods and other severe weather prompted Gov. Haley Barbour to declare a state of emergency in several Mississippi counties, including Union, Benton, Lafayette, Tippah and Panola.
Between Friday afternoon and Sunday, eight to 10 inches of rain had fallen in Northeast Mississippi, a possible record for some parts of the area, according to the National Weather Service.
Branda said the rainfall was equivalent to what a hurricane or tropical storm might produce upon landfall in Mississippi.
It certainly appeared that way in Prentiss County.
"There's more water than I've ever seen," said Prentiss County Emergency Management Director Ralph Lauderdale. "The flooding is pretty well all over the county."
In Alcorn County, where the weather was blamed for the death of a motorist who drove into a ditch, the Red Cross opened a shelter at Corinth's Crossroad Arena.
Red Cross Executive Director Patty Tucker reported that 19 people had shown up by early Sunday night.
The Corinth Fire Department conducted boat rescues at Combs Court apartments on Cass Street and Melody Park near Proper Street, and evacuated Kmart and Kroger stores near Fulton Drive.
Tupelo Schools Superintendent Randy Shaver said Rankin and Thomas Street Elementary Schools, as well as the middle school, experienced some flooding, but crews were able to clean up the water.
All Tupelo and Lee County schools will be open today.
The flooding in Union County damaged some schools in the New Albany district, but Superintendent Charles Garrett said, superintendent of New Albany schools, said the schools had some flooding, but that school would open Monday.
He said water had seeped in under some doors, and the middle school cafeteria's roof had leaked. Custodial staff, coaches and some administration were at the schools Sunday to clean up the water, he said.
Also affected by the powerful storms was road and highway travel.
Police in Tupelo, where a teen-ager died in a weather-related automobile accident Sunday afternoon, spent much of the day closing streets and redirecting traffic away from flooded areas.
Closed were parts of South Thomas Street, Lumpkin Avenue, Crossover Road and North Gloster Street.
At least three automobile accidents on North Gloster Street were caused by the flooding. One person was taken to the hospital for minor injuries.
In Lee County, Sheriff Jim Johnson said flooding washed out a bridge on County Road 2848 and caused deputies to close Old Saltillo Road in order to let water levels fall.
Mississippi Highway Patrolman Ray Hall said several highways were filled with water, especially U.S. Highway 72 near the Tippah and Alcorn County lines.
On state Highway 4 in Benton County between Ashland and Holly Springs, rushing waters washed out the highway, closing it until possibly Tuesday.
In Pontotoc County, the weather forced the closing of West Reynolds Extended, Cane Creek Road and a portion of U.S. Highway 178 in Sherman for at least part of the day.
Daily Journal reporter Chris Kieffer contributed to this story.