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Snow, frost possible for some as cold air plunges into Ontario

Wednesday, October 5th 2022, 8:22 pm - A 10-degree temperature drop will hit parts of Ontario this week as Arctic air sweeps southward, potentially bringing a transition from rain to some snowflakes.

Make the most of Thursday’s pleasant temperatures—a huge change is on the way for southern Ontario and Quebec.

A cold front plunging into the region will send temperatures tumbling by Friday, with single-digit highs more akin to what you’d expect to see in November. Adding insult to the chill is that this change could bring the first taste of frost and wet snow for parts of Ontario as we move into the long Thanksgiving weekend.


DON’T MISS: Canada’s October outlook: what you can expect this month


This week: Late summer-like warmth ahead of the coolest air of the season

Thursday is the last day we’ll see comfortable temperatures across Ontario and Quebec before an abrupt plunge into fall sweeps through the provinces.

If you’re not a fan of cooler weather, blame it on the Pacific Ocean. The track of a typhoon in the western Pacific altered the jet stream enough to deepen the trough responsible for this forthcoming blast of cold air.

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This potent front will track across Ontario and Quebec, producing showers and gusty winds, and ushering in a dramatic drop in temperatures. Wet snow is possible for some higher elevations in northern Ontario by early Thursday, as temperatures dip down to the freezing mark.

Models have been slowly reducing the amount of snowfall that could accumulate on the ground, so there is a greater chance the wet snow that falls will not accumulate with this event.

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What is most likely at this point is that some lake-effect rain showers will develop off of Georgian Bay and Lake Huron. If temperatures cool enough, however, some of that rain could transition to mixing or some wet flurries, more likely in higher elevations early Saturday morning in southern Ontario.

Overnight lows this week will bring a likely frost in some areas, so make sure to protect your plants. The risk will become more widespread at the end of the week.

Friday is going to be the coldest day many of us have seen in months. November-like weather arrives to end the week with high temperatures remaining in the single digits for much of the region.

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If Toronto only reaches 11°C on Friday, it’ll be the city’s first 11-degree high in 169 days: Our last daytime high of 11°C or below was a chilly 4.2°C reading on April 27.

Chilly weather will remain for the start of the long weekend, but temperatures should rebound somewhat to near seasonal as it progresses. However, there is the potential for a couple days of milder weather during the following week.

Will the pattern shift in October?

As October progresses, there are several signals in the global pattern that support a shift in the cool pattern, which would allow the warmer than normal weather in the west to spread back east into Eastern Canada, according to Dr. Doug Gillham, a meteorologist at The Weather Network.

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"However, our forecast confidence for the middle and end of October is lower than normal," said Gillham in The Weather Network's October outlook.

But, we still think that the second half of October will bring periods of milder weather, but we are also concerned that the early pattern will continue to show up at times during the latter portion of the month.

WATCH: The best time for you to switch to winter tires

Check back for the latest on conditions across Ontario and Quebec.

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