It was slow-going on parts of Hwy. 402 Tuesday morning as persistent snow streamers off Lake Huron impacted the Watford and Strathroy areas.
OPP say road surfaces became very slippery due to drifting and blowing snow, resulting in multiple collisions.
No injuries have been reported.
West Region OPP Sergeant Dave Rektor says trucks and other vehicles were being removed from the ditch and median causing traffic delays through the morning hours.
"There's a lot of crashes on the go, but nothing serious so that's good news," Rektor said in Tuesday morning Periscope video on Twitter.
The westbound lanes of Hwy. 402 were closed late Monday night after a tractor trailer jack-knifed at Oil Heritage Rd.
Monday's storm system dumped about 10 cm (4 inches) of snow in the Sarnia-Lambton area, including Forest where strong winds caused drifting and poor visibility. School buses in Zones 1 and 4 in the Forest and Petrolia areas were cancelled Tuesday because of the weather.
Exams for high school students in Sarnia-Lambton in both the public and separate school boards were delayed one day.
Environment Canada says the south end of St. Catharines got the most snow, 27 cm, nearly a foot.