Police say they have closed Highway 400 in both directions due to a series of vehicle collisions.
Ontario Provincial Police have shut down the major artery from Highway 88 outside of Bradford, Ont., to Mapleview Drive in Barrie, Ont.
Whiteout conditions on the highway north of Toronto have limited visibility and made driving treacherous.
Police and paramedics are on the scene, although they say no serious injuries have been reported yet.
Sgt. Kerry Schmidt of the OPP estimates that dozens of vehicles have been involved in accidents on the 30-kilometre stretch of Highway 400.
Schmidt says that police have begun to remove cars from the road, but they're asking commuters to avoid the area as high winds and poor visibility continue.