Flooding has forced the closure of one of Toronto's main arteries, with police diverting traffic off of Don Valley Parkway as heavy rain soaks the city.

Toronto and surrounding areas are under a flood warning, with rising water levels causing potentially "hazardous" conditions, ahead of freezing rain overnight.

The DVP has been closed southbound as a result of excess flooding form the Don River, police say, adding vehicles are being forced to exit at the Bayview/Bloor off-ramp.

The Toronto and Region Conservation Authority says flooding is already occurring in parts of Brampton and on roadways in Woodbridge in Vaughan. Water levels are also on the rise near the Don Valley Parkway and other low-lying roads.

"Current watershed conditions are saturated," the TRCA said. "The heavy rain and rise in temperatures to above zero today will increase the potential for ice jams."

Hydroplaning, power outages

In some parts of Toronto, police have seen cars hydroplaning. Approximately 2,300 customers were briefly affected by power outages but Toronto Hydro says it was able to restore power more quickly than expected.

The city also remains under a rainfall warning with Environment Canada saying between 40 and 60 millimetres of rain could fall by Saturday evening. The amount could easily break records, according to meteorologist Gerald Cheng.

"It's going to be slippery," Cheng told CBC Toronto Saturday. "Be careful out there when you're on the roads."

As of 1:30 p.m. on Saturday, Environment Canada says 23 millimetres of rain had been recorded at Toronto's Pearson International Airport.

On Jan. 9, 1946, a total of 58.7 millimetres of rain fell on Toronto, setting a record for the most rain in any day in January in the city.

Toronto is under a rainfall warning and Environment Canada says between 40 and 60 millimetres of rain could fall on the city by Saturday evening. (Muriel Draaisma/CBC)

Freezing rain forecast to hit Toronto around midnight

The rain is forecast to turn into freezing rain around midnight.

Environment Canada expects Toronto to get about six hours of freezing rain overnight.

Light snow is then expected to fall on Sunday before stopping sometime mid-morning.

Crews are very busy opening catch basins around the city which is helping move water off the roadway and reducing ponding. If you see crews working please give them space. <a href="https://twitter.com/cityoftoronto?ref_src=twsrc%5Etfw">@cityoftoronto</a> <a href="https://twitter.com/311Toronto?ref_src=twsrc%5Etfw">@311Toronto</a> <a href="https://t.co/NvfvNWRgHX">pic.twitter.com/NvfvNWRgHX</a> —@TO_Transport

Also on Sunday morning, residents should brace for strong southwest winds that could gust up to 60 kilometres per hour. The wind will signify the end of the precipitation, Environment Canada says.

Motorists are urged to turn on lights if visibility is reduced and to maintain a safe following distance.

City restricts lanes in some areas in Toronto

In Toronto, the city reported ponding or high water in the following areas:

Keele Street and Finch Avenue.

In the eastbound curb lane at Wilson Avenue near Jethro Road. It says lanes may be restricted due to the water on the roads.

Ellesmere Road.

Lake Shore Boulevard West between Rees Street and Parliament Street. Lane restrictions are in effect.

In Peel region, police say the following roads are closed due to flooding:

Southbound Winston Churchill Boulevard from Mayfield Road to Wanless Drive.

Eastbound and westbound Wanless Road from Winston Churchhill Boulevard to Heritage Road.

Southbound and northbound Wanless Drive to Bovaird Drive.

In York region, the following roads were closed:

Donald Cousens Parkway at 17th Avenue

Old Homestead Road from Queensway North to Woodbine Avenue

Broda Drive at Highway 27

UPDATE:<br><br>- please plan alternate routes into your travelling plans today <a href="https://t.co/mj7z4v1eMo">pic.twitter.com/mj7z4v1eMo</a> —@PeelPolice

Forecast meets criteria for winter rainfall warning

Because the ground is frozen in parts, it has a reduced ability to absorb the rainfall. Environment Canada said the forecast meets the criteria for a winter rainfall warning because it is calling for more than 25 mm of rain in 24 hours.

Lane restrictions in effect on Lake Shore Boulevard West between Rees St. And Parliament due to ponding. Some ponding along Ellesmere Rd. Please travel according to conditions and try to avoid areas of ponding. If there are workers present please proceed with caution. <a href="https://t.co/d3oUsjhL9P">pic.twitter.com/d3oUsjhL9P</a> —@TO_Transport

Significant rainfall expected throughout the day. Please walk, bike and drive with caution. Motorists and cyclists should be extremely cautious around areas of high water/ponding. Drivers please slow down and drive according to road and weather conditions. <a href="https://t.co/2Zr58Caak9">pic.twitter.com/2Zr58Caak9</a> —@TO_Transport