Remnants of tropical storm Debby were expected to bring up to 120 millimetres of rain to parts of Eastern Canada as they merge with another low pressure system over the Great Lakes.
The storm system has started passing through southern Ontario and Quebec today, prompting Environment Canada to issue alerts and warnings for communities between Cornwall, Ont., and Quebec City about the risk of flash flooding.
By 10 a.m., between 60 and 80 millimetres had already fallen in Montreal with more expected later in the day.
Revised forecasts show the Montreal area receiving 80 to 120 millimetres by the end of the day — with some locations in southwestern Quebec expected to receive as much as 140 millimetres.
Quebec's Transport Department warned of some flooding on highways and temporary road closures due to the torrential rain.
Environment Canada has warned that minor landslides are possible.
Ottawa was also forecast to be soaked, with 50 to 100 millimetres of rainfall expected through the day.
In Toronto, between 25 to 50 millimetres of rain is expected to fall through the morning and early afternoon.
The remnants of Debby are expected to reach New Brunswick by evening and dump up to 40 millimetres of rain through Saturday morning.