The agency issued a freezing rain warning for the city at 4:42 a.m. on Saturday.
In the statement, Environment Canada said the storm is likely to start on Saturday afternoon or evening and last into Sunday morning.
The freezing drizzle is set to turn into rain on Sunday morning, with a high of 2 C expected for the day.
This weekend's expected ice storm comes one week after a blast of wintry weather dumped around 20 centimetres of snow on the city.
Cooler temperatures and a mix of sun and clouds are in the forecast for the early part of next week. Highs of -6 C and -9 C are expected for Monday and Tuesday, respectively.
The freezing rain warning is in effect for much of the southern and eastern regions of the province.
A significant frontal boundary from Sarnia to near Hamilton and eastwards across Lake Ontario is expected to remain fairly stationary for another day.
Some areas north of the front are expected to get up to 20 millimetres of freezing rain, while others could get snow, ice pellets or rain.
Forecasters say travellers should be prepared for dangerous winter conditions and possible power outages.