Southern Ontario is in for what Environment Canada calls a weather "rollercoaster" in the next few days while falling temperatures are already causing problems in the northeast.

A warm front moving in from Colorado brought balmy, often double-digit temperatures to southern Ontario on Wednesday, and the agency said it was expecting many areas to set new weather records.

Toronto and London hit record highs of 14 C on Wednesday morning while Windsor saw a 15 C high early in the day, shattering the Jan. 30 record of 9.5 C set in 1988. Temperatures were moving downward again by afternoon.

David Phillips, a senior climatologist with Environment Canada, said Toronto has seen erratic and highly unusual weather this month, culminating with Wednesday's unseasonable warmth.

"It's about 15 degrees warmer than it should be for this time of the year," he said.

Rain was also expected across southern parts of the province -- up to 40 mm in some areas -- prompting officials in London to warn of potential flooding.

But Environment Canada warned winter will be back with a vengeance Thursday, with the mercury plunging to below freezing as an Arctic cold front moves in overnight.

In northeastern Ontario, rainfall and freezing rain warnings are in effect for the greater Sudbury area, New Liskeard and North Bay.

Ice-slicked roads were so treacherous Wednesday morning the provincial police closed all provincial highways into and out of Sudbury but had re-opened them by mid-afternoon.

In other parts of the northeast, winter storm warnings are in effect for Timmins, Cochrane, Iroquois Falls and Kirkland Lake.