The City of Toronto says it is taking steps to prepare for what is shaping up to be a significant rain storm over the weekend.

Environment Canada issued a rainfall warning for Toronto and much of southern Ontario on Friday, warning that a system from Texas will bring heavy rain and strong winds on Saturday with the possibility of freezing rain.

The national weather agency says light rain or drizzle on Friday will continue Saturday morning and will be heavy at times.

The rain is expected to persist all day Saturday and may change over to freezing rain beginning Saturday evening as temperatures dip closer to the freezing mark.

The agency says a freezing rain warning may be issued as the storm moves through the region.

Total rainfall amounts of between 40 and 60 mm are possible, Environment Canada says.

“Travel will be impacted throughout Southern Ontario Saturday into Sunday," Environment Canada said in its weather advisory.

On Friday night, the weather agency also issued a fog advisory for Toronto and the GTA.

"Dense fog has developed over the regions," the statement said. "As a result, visibilities will be reduced to less than 200 meters."

The fog will slowly dissipate when the rain arrives overnight.

Power outages possible due to high winds

City staff say Toronto Water will be available around-the-clock to respond to flooding calls along with forestry crews, which will be on standby to deal with fallen trees and branches.

Transportation Services staff will be assisting in the city's storm response by monitoring road conditions and  patrolling to clear debris and clear catch basins.

"We’re not seeing any cold temperatures so we don’t anticipate much freezing in Toronto but there will be, we anticipate, high winds so branches are a potential for coming down, taking down power lines," City of Toronto spokesperson Brad Ross said Friday.

"Basement flooding is a concern. There are a number of things residents can do. They can help us by clearing catch-basins around their homes. If they have drainage near their home to make sure those are clear of any debris."

City staff is also reminding residents to be patient when calling 311 to report issues as higher than normal call volumes could result in delays.

Rain has 'no place to go'

Environment Canada Senior Climatologist Dave Phillips says the weather on Saturday could break more than one record.

Phillips said the rainfall record for Jan. 11 is around 25 millimetres and the high temperature record is 11.7 C.

Environment Canada is calling for a high of 11 C on Saturday.

“This is a real powerhouse storm. We are going to see almost everybody in Eastern North America… affected by this,” Phillips told CP24 on Friday.

He noted that if the precipitation was snow instead of rain, Toronto might have seen upwards of 30 centimetres of snowfall this weekend.

“The city would maybe be calling out the army,” Phillips said. “The rain you can deal with.”

He said widespread power outages and flooding are a possibility given the amount of rain that is expected to arrive in a 24-hour period.

“Even the part of the (ground) that isn’t frozen is sopping wet and so this added moisture that we see… has got no place to go,” Phillips added.

“We could see flash flooding if the amount of rain is very intense at times. We could certainly see some river flooding.”

The Toronto and Region Conservation Authority (TRCA) has issued a Watershed Conditions Statement ahead of the rainfall, noting that all shorelines, rivers and streams within the GTA "should be considered hazardous."

"All rivers within the GTA may experience higher flows and water levels, resulting in potential flooding and hazardous conditions, especially behind bridges and culverts where ice jams are present," the TRCA said.

"Ponding may occur in low-lying areas. The combination of slippery and unstable banks could create hazardous conditions close to any river, stream or other water body."