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A tale of two seasons in Ontario with summer-like warmth and snow

Monday, October 3rd 2022, 7:53 pm - A lobe of cold Arctic air will dive south late week following a sweeping cold front Thursday that will contribute to temperatures plunging 10 degrees cooler on Friday

While the week will start with a comfortable temperature climb in southern Ontario, it won't have a pleasant finish. After late-summer-like warmth surges into the region by Wednesday, a cold front hot on the trails will bring an abrupt end to the 20-degree temperatures, sending daytime and overnight values into the single digits by Friday. To make it feel worse, there could be snow in parts of the region as we head into the start of the long weekend. For more, read below.


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


This week: Uptick in temperatures before freefall with snow chance

The gradual warming trend across Central Canada will peak on Wednesday as temperatures reach or exceed 20°C in southern Ontario and Quebec, with upper teens to near 20°C in the National Capital Region.

NATPATTERN

Comfortable conditions won’t last long, though, as the cold front plows into the region on Thursday.

As well, the track of a typhoon in the western Pacific last week contributed to the depth of trough in the jet stream associated with this forthcoming blast of cold air.

OntarioLobe

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 even likely for parts of northern Ontario by early Thursday, including the higher elevations near Thunder Bay and towards Timmins, as temperatures dip into the low- to mid-single digits.

Wet snow will attempt to spread across northeastern Ontario later in the day Thursday before the cold front slides across southern sections.

"There is some uncertainty how far south the snow spreads," says Kelly Sonnenburg, a meteorologist at The Weather Network. "Late Friday into Saturday morning parts of northern cottage country could also see some flurries flying mixed within some cool rain. The question lies in if southern Ontario cools enough to see snow overnight into Saturday morning."

ONSNOW

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.

ONTEMPFRI

If Toronto only reaches 10°C on Friday, it’ll be the city’s first 10-degree high in 169 days: Our last daytime high of 10°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.

MIDLATEOCTPATTERN

"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: Why you can't rule out tornadoes during Ontario's cooler months

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

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