Police are warning drivers to slow down and be aware of their surroundings ahead of a sudden drop in temperatures that could make for an icy afternoon commute.

The temperature reached a high of 11.9 C at 6 a.m. but a cold front moving into the city will cause temperatures to plummet later this morning.

According to Environment Canada, the temperature will drop below the freezing mark by 1 p.m. and continue to fall throughout the afternoon, reaching a low of – 10 C by late tonight.

Freezing rain mixed with ice pellets started to fall in downtown Toronto at about 1 p.m.

In anticipation of the frigid temperatures, Toronto's medical officer of health has issued an extreme cold weather alert, triggering additional services for the homeless. Environment Canada has also issued a special weather statement warning of a “brief period” of freezing rain as the precipitation changes over to snow.

“Right now the roads are going to be OK but in a couple of hours we will be getting close to that freezing point and on any elevated expressways, such as the Gardiner, you will see a temperature cool down much faster than the rest of the roadway,” Const. Clint Stibbe told CP24 on Friday morning. “You could be in a situation where it is wet in one spot and ice at the next, so you need to make sure you are dropping your speeds especially when you notice ice or glaze appearing on the roadway. Paying attention is going to be key.”

Flooding on parts of DVP and Bayview Avenue overnight

The return of the extreme cold comes after an extended period of mild, record-breaking weather and steady rain.

On Thursday, the temperature reached 12.6 at Pearson International Airport, melting snow banks and breaking a 43-year-old record for January 11th.

The mild weather and rain resulted in a portion of the Don Valley Parkway and Bayview Avenue flooding overnight after the Don River overflowed its banks.

The flooding began at around midnight, likely hastened by a backup of ice at the foot of the Don River.

The northbound lanes of the DVP were initially closed from the Gardiner Expressway to Dundas Street; however those lanes reopened at around 5:30 a.m. The southbound lanes were closed at Bloor Street but that closure was lifted at around 6 a.m.

Bayview Avenue, meanwhile, was closed in both directions between River Street and Eastern Avenue but also reopened at around 6 a.m.

At one point, the floodwaters had submerged GO Transit’s Richmond Hill line tracks however they resided in time for service to start as scheduled. Metrolinx spokesperson Anne Marie Aikins, nonetheless, told CP24 that officials would be “monitoring” the situation throughout Friday morning as the rain was expected to continue falling for several hours.

“Until a few moments ago we weren’t even going to be able to ruin our Richmond Hill line. That is ok for now but we have to keep monitoring that flooding,” she said.

TRCA issued flood warning

The flooding came after temperatures rose to unseasonably warm levels in recent days. Those temperatures, combined with the approximately 10 millimetres of the rain the city received, melted snow banks and caused the water levels in the Don River to rise suddenly.

Shortly after midnight, the Toronto and Region Conservation (TRCA) issued a flood warning due to what it said were “hazardous conditions,” though it later downgraded the warning to a flood outlook.

"Although the water levels within TRCA’s rivers and streams are receding, the water levels are still higher than usual and river and stream banks remain slippery maintaining dangerous conditions," the flood outlook, issued at 7 a.m., reads. "Ponding may still occur in low-lying areas. The combination of slippery and unstable banks, cold water temperature, and the potential for ice jamming could create hazardous conditions close to any river, stream or other water bodies."

Cold front on the way

Environment Canada says that the city will receive another 5 millimetres of rain today before the temperatures plummet to a low of – 12 C by tonight.

In anticipation of those temperatures, Toronto's medical officer of health has issued an extreme cold weather alert, triggering additional services for the homeless.

Speaking with CP24 on Friday morning, OPP Sgt. Kerry Schmidt double down on Stibbe’s warning to drivers.

“It is beautiful right now, it feels warm and balmy, almost spring-like but as the afternoon and evening comes we could certainly have a lot of slippery and icy conditions, especially on those overpasses and bridges,” he said. “Always keep in mind when you are taking those on ramps and off ramps that there could also be slippery sections on those as well. If you are going to fast you may not be able to make that corner and will end up in the ditch.”

As of 7 a.m., about 10.5 per cent of all arriving flights and 11.8 per cent of all departing flights at Pearson International Airport had been cancelled, though the Greater Toronto Airports Authority told CP24 that they were ready for the changing conditions.

”The forecast is calling for some mixed precipitation today, but given where we are located, we are no stranger to snow and freezing rain and have fully trained staff on call 24/7 to ensure runways are kept clear and safe for takeoff and landing,” the GTAA said in a statement. “We can’t predict what the impact of weather will be, but we do have the appropriate equipment and teams ready.”