An ice storm warning was issued from the Smoky Mountains, northward through Knoxville, Cumberland Gap and well into Kentucky. The National Weather Service said ice accumulations up to 0.10 inch per hour were expected into the afternoon Friday.
Forecasters cautioned that driving was treacherous and that icing could bring down tree limbs and power lines.
Although ice was beginning to melt in Middle Tennessee by midmorning on Friday, Tennessee Emergency Management Spokesman Jeremy Heidt said the state Highway Patrol was working 20 separate wrecks in the Clarksville area.
Heidt said there are also multiple wrecks in East Tennessee due to ice on the roads. State officials are working with Kentucky to try to stop motorists from traveling into the areas of Tennessee that are the most icy or congested from earlier wrecks.
Meanwhile, the Transportation Department was salting roads to try to melt the ice.
The governments of Knoxville and Knox County told employees not to come to work, unless their jobs were essential for safety.
Most school systems in East Tennessee called off classes early Friday, as did several on the Cumberland Plateau.
Freezing rain advisories and winter weather advisories covered counties outside the ice storm zone.