People in the north-central part of the Canadian province of Ontario are digging out after one of the worst snow storms on record.

Some areas north of Toronto received as much as 100 centimetres of snow over the past three days.

The main highway through the region re-opened for the first time in days, but nearly all side roads remain closed, blocked by a thick blanket of snow, in some areas chest high.

More than 100,000 people have been affected by the storm, either cut off in smaller communities, or in their cottages, or stranded by the road closures.

In one town the mayor declared a snow emergency, shutting schools and businesses.

Officials say emergency road crews clearing roads are completely exhausted. Officers at one police detachment said they could not see their parked patrol cars buried under the snow.

Police are also urging travellers to stay away from the region at least for the next couple of days.

Meanwhile, western Canada is in the grip of a cold snap with temperatures plummeting anywhere from -40 to -50 degrees Celsius.