Environment Canada is warning that freezing rain could bring power outages and significantly affect transportation in Waterloo Region and Wellington County.
The weather agency issued a freezing rain warning for Wednesday for much of southwestern Ontario, including Waterloo Region, London, Hamilton, Niagara and Toronto.
A cold front is expected to move into southwestern Ontario Wednesday morning and then stall over regions near Lake Erie while at the same time a strong Colorado low will move northeast along the cold front, according to a statement from the weather agency.
The cold air will cause temperatures to drop Wednesday evening, which will likely see the development of freezing rain.
Ice could accumulate on untreated surfaces, as much as to 15 millimetres, according to Environment Canada.
The freezing rain is expected to change into rain going into Thursday morning.