Toronto under special weather statement ahead of heavy rainfall

CP24's weather radar shows a system that is expected to bring heavy rainfall to the Toronto area on Friday morning. (CP24)

A special weather statement is in effect for Toronto with heavy rainfall expected over the Golden Horseshoe in the next 24 hours.

Environment Canada is warning of a significant rain event that may impact urban centres in Eastern Canada, including Ottawa, Montreal, and potentially Toronto.

Parts of southwestern Ontario and Toronto could see between 25 and 50 millimetres of rainfall between Thursday and Friday night, according to the national weather agency.

Parts of Quebec and the Maritimes could see upwards of 100 millimetres of rainfall, the national weather agency said.

During a virtual news conference on Thursday afternoon, Jennifer Smith, Environment and Climate Change Canada’s national warning preparedness meteorologist, said heavy downpours could cause localized flooding in urban environments.

“Significant impacts may occur in large urban centres, such as Ottawa and Montreal, and possibly even Toronto, especially if a heavy shower develops over a prone area,” Smith said.

She noted that two weather systems are expected to merge, creating a significant amount of moisture in the atmosphere.

“You’ve got an existing system over the Great Lakes… and we’ve got a lot of moisture coming in associated with the remnants of (tropical storm) Debby,” Smith added.

“So the two are essentially feeding off of each other in the sense that we are supplying an existing system with a lot of moisture. And this is going to give the atmosphere the potential to develop that into showers and thunderstorms and heavy rain for us.”

Smith urged those in affected areas to keep an eye on weather alerts.

“There could be localized flooding just due to urban environments not having efficient drainage for rainfall in a short period of time,” she said.

“We have already seen a lot of precipitation in Eastern Canada this past summer so everything that could absorb more water is already saturated. So over land flooding and what not is likely as a result.”

Just three weeks ago, Toronto experienced widespread flooding and power outages after nearly 100 millimetres of rain fell within a three-hour period.

Sections of the Gardiner Expressway and the Don Valley Parkway were closed after the busy roadways became inundated with water, stranding some motorists.

The deluge flooded basements, subway stations, and a retail concourse at Union Station.

“Just be mindful that there is flash flooding. It can cause pooling on roads, it is dangerous to be out on the water,” Smith said ahead of the impending storm. “Just be mindful of the environment that it is creating and make your plans accordingly.”