I did a search on environment Canada's web-site and came up with:
"Toronto's Snowstorm of the Century - January 2-15, 1999. A series of storms stalked the city, dumping nearly a year's amount of snow in less than two weeks. In all, the city recorded the greatest January snowfall total ever with 118.4 cm and the greatest snow on the ground at any one time with 65 cm. The storms cost the city nearly twice the annual budget in snow removal."
Largest single dumping they've shown is also in Tornoto:
"Toronto's Worst Single-Day Snowfall - December 11, 1944. A severe winter storm dumped 48 cm of snow on Toronto's downtown, while gale-force winds piled the snow into huge drifts. A total of 57.2 cm fell over two days. In all, 21 people died -- 13 from overexertion. Funerals were postponed, expectant mothers walked to hospitals, and there were no home deliveries of milk, ice or fuel. Of major concern, factories producing war ammunitions had to close temporarily."
If you want to have a read-through yourself, here's the link:
http://www.ec.gc.ca/press/vote20_f_e.htm
Keep in mind, these are Toronto records - and I've listed these and they were the only Ontario mentions there.