A winter storm wreaked major havoc on the roads in the London area on Wednesday.

Environment Canada was calling for about 10 to 20 centimetres of snow and a snow squall warning remained in effect for London, as well as Middlesex, Elgin, Huron and Perth counties for much of the day.

Whiteout conditions were reported on many highways and in-town routes.

London police. St. Thomas police and OPP asked residents to stay off the roads altogether if possible due to poor visibility. 

Cars were left stranded on many highways, especially to the east of the city.

OPP Sgt. Dave Rektor says those who got stuck faced a long wait for assistance. He says there were over 70 collisions reported in the area in a two-hour span Wednesday morning.

The OPP is advising people to pack an emergency kit and make sure they have a fully charged cell phone.

There were numerou road closures in the region on both county and city streets, as well as on 400 series highways, including the 401, 402 and 403.

Numerous events and meetings have also been cancelled across the region, and anyone with plans should call ahead to ensure the event is still taking place.

Open water partly to blame

The fact that Lake Huron remains largely unfrozen - it has only about 11 per cent ice cover - means cold winds sweeping over warm water creating snow squalls.

Officials are asking residents, especially in midwestern Ontario, to ensure furnace vents aren't blocked by snow.

It remains unclear how long it will take for the frigid temperatures to help the lake freze over and reduce the volume of snow in the squalls.