Mild and rainy Monday quickly changes back to snow in Ontario. Risk of 5-15+ cm
A cold front moving through southern Ontario will bring thunderstorms, a temperature drop, and lake-effect snow by Monday night, with up to 30 cm expected in the snowbelt in the coming days
While northern Ontario faces a significant winter storm with more than 50 cm of snow possible, southern regions are also feeling some effects from the low-pressure system.
DON'T MISS: A potentially strong El Niño will develop by this summer
Mild, rainy conditions on Monday will shift to snow overnight, with 5-10 cm expected widely, and localized amounts of 10-25 cm possible. Strong winds and heavy snow could create challenging travel conditions and reduced visibility. Some areas may see temperatures drop sharply by 20°C to 25°C within 12 hours following the cold front passage.
Be sure to keep an eye on the road conditions before heading out.
Temperature drop and snow follows behind cold front
A powerful cold front will sweep across southern and eastern Ontario on Monday, packing a mix of weather over a span of 24 hours.
The day began with mild temperatures reaching the low double digits in some areas, including the Greater Toronto Area (GTA) and Ottawa, accompanied by showers. However, conditions changed rapidly on Monday afternoon.
A line of thunderstorms is forecast to develop and move from Kingston to Ottawa through late Monday afternoon, bringing small hail, strong wind gusts, and heavy downpours.
By the evening, winter weather will make a quick return. As temperatures fall sharply—by as much as 20-25°C in places like Ottawa, Brockville, and Cornwall—rain will transition to snow.
Frozen surfaces from rapidly dropping temperatures and refreezing puddles may lead to slick and hazardous conditions, with widespread 5-10 cm of snow expected from the eastern GTA to Ottawa by Tuesday morning.
Evening commutes could be impacted by bursts of heavy snow, while wind chills dip into the minus teens by Tuesday.
WATCH: Ontario Weather Whiplash: Snow and strong winds to follow mild morning
Lake-effect snow will develop downwind of Lake Huron and Georgian Bay late Monday, with localized accumulations of 10-25 cm possible in the snowbelt regions under a snowsquall watch.
Strong winds of 60-80+ km/h across southern Ontario, Niagara, Kingston, and Cornwall may contribute to reduced visibility and difficult travel, potentially resulting in road or school closures on Tuesday.