Mississauga has swung from spring-like warmth to the threat of the season's biggest snowfall in less than a week, and the wild weather turned deadly on Friday in Port Credit.

On Wednesday, Jan. 14, Environment Canada issued a yellow snowfall warning for Toronto and surrounding regions, including Peel. The agency said 10 to 20 centimetres of snow could fall starting Wednesday night and lasting into Thursday afternoon, with reduced visibility from blowing snow.

Cold follows the snow

Environment Canada also warned of a sharp drop in temperature. In the Toronto area, it could fall to about -9 C on Thursday morning and feel closer to -22 with the wind chill.

Thursday's morning commute is likely to be impacted by snow.

— Lyndsay Morrison, CTV News Toronto weather anchor

If the forecast holds, it could be the snowiest day of the winter so far at Toronto Pearson International Airport in Mississauga, where the largest single-day total this season had been 12 centimetres on Dec. 26.

A record on Friday

The snow follows a remarkably mild stretch. On Friday, Jan. 9, Pearson recorded a high of 14.1 C, breaking the previous Jan. 9 record of 11.6 C set in 2008. A special weather statement that day warned of wind gusts up to 90 km/h across the Toronto area.

The winds proved fatal in Port Credit. Peel Regional Police said officers and paramedics were called to the area of High Street East and Lakeshore Road East at about 2:30 p.m. Friday, where a woman in her 80s had been struck by a tree branch that police said came down because of the high winds. She was taken to hospital with life-threatening injuries and later died.

Ice and high water

On Saturday, Jan. 10, Peel Region was briefly placed under a special weather statement for freezing rain before Environment Canada lifted it for the area. Communities in York and Durham regions faced icier conditions that evening.

The swings in temperature have also raised concerns around local waterways. Credit Valley Conservation, which oversees the Credit River watershed, warned this week that ice on rivers, ponds and lakes can look solid but be unsafe, and that rain and melting snow can raise water levels and speed up flows.

Stay off the ice and keep children and pets away from shorelines.

— Credit Valley Conservation

The conservation authority reminded residents that stormwater ponds were not built for skating and that ice thickness on them can change because of road salt and shifting temperatures. Anyone who sees someone fall through the ice should call 911 immediately, since trying to rescue a person or pet from ice is dangerous.

Getting ready

Drivers should plan for a slow commute Thursday, clear snow and ice from vehicles before leaving and leave extra space between cars. Pedestrians should watch for icy patches as temperatures fall overnight. Current alerts for Mississauga are posted on Environment Canada's weather website and the WeatherCAN app.