High winds heavy rain and large hail were also reported in 21 states from New York to Arkansas, according to the US Storm Prediction Center.
In Alabama, where at least 45 people have died, Governor Robert Bentley called out the state's National Guard to deal with heavy damage reported in 18 counties.
The Tennessee Valley Authority shut all three reactors at the Browns Ferry nuclear plant in Alabama, and Washington is to send the state search and rescue assistance.
States of emergency were aslo declared in Arkansas, Kentucky, Mississippi, Missouri, Tennessee and Oklahoma.
Storm victims across the south were trapped in their homes, amid flattened buildings and overturned vehicles. Many roads were blocked by fallen trees or power lines.
Much of the southern United States had been complaining of drought, and only last weekend, Governor Rick Perry of Texas declared a period of prayer for rain in his state.
Its thought the number of people killed in these tornadoes in the United States is the highest since 1974, when 310 died.