The southbound side was closed between Primm Road and Baker Street shortly after noon. The Nevada Highway Patrol said there was no time frame for when the closure would be lifted.
The agency warned drivers to expect major delays if they are attempting to travel between California and Nevada.
Shortly thereafter, the California Highway Patrol in Barstow said both sides of the 15 were shut down. Also, the San Bernardino County Fire Department said there were several traffic collisions due to weather in the area.
CHP tweeted a little after 3:30 p.m. that the highway was reopened.