Reports of accidents came from across the Niagara Region after freezing rain and ice pellets began falling shortly after noon.
At the corner of Thorold Stone and Garner roads, three vehicles were involved in collisions.
The most serious was a rollover involving a northbound Ford Escape which wound up in the ditch on the north side of Thorold Stone Road.
Also northbound, but on the south side of Thorold Stone Road, a Saturn and Chevy van were involved in a minor collision.
There is no word on injuries at this time.
An earlier one-vehicle collision in Thorold occurred at the corner of Merrittville Hwy. and Seburn Road.