Ontario to endure wild temperature swing, thunder risk this week

It’s a week of all seasons across Ontario this week as record warmth and a chance for thunderstorms give way to a dramatic cooldown and the risk for snow

What a week we’ll have across Ontario as the atmosphere churns up some wild extremes across the province.

Above-seasonal warmth building for the first half of the week could threaten all-time high temperature records for the month of February. Dynamics may even be favourable for some thunderstorms.

An abrupt change follows soon after as a cold front slices across the Great Lakes. We’ll see a tremendous temperature drop through Wednesday night that could rival some of the most dramatic cooldowns in recent memory.

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Warmth builds on Monday and Tuesday

This week begins with an upper-level ridge building over the Great Lakes and a broad low-pressure system churning over the U.S. Midwest. These features will work together to send temperatures soaring to levels more common of late April than late February.

Toronto February 2024 temps through Feb 24

A typical February in Toronto struggles to hit the double-digits just once. This year, though, we’re on track to see our sixth and seventh days reach 10°C or warmer.

Monday’s highs will poke into the double digits across portions of southwestern and northwestern Ontario.

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Windsor and London could climb up to 11°C on Monday, while Fort Frances to the northwest could challenge its all-time February temperature record of 13.2°C—a benchmark set back in mid-February 2017.

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Ontario Tuesday Afternoon Temps

Temperatures soar even higher on Tuesday across all of southern and eastern Ontario. Locations downwind of the lakes will stay much cooler, while inland communities will enjoy readings well into the mid-teens.

We’re closely watching eastern Ontario for potential all-time February heat records. Ottawa’s warmest February temperature was a balmy 12.4°C day back in 2000.

Communities along Highway 401 like Brockville and Cornwall could see readings as high as 17°C on Tuesday as warmer winds blow out of New York, which is about 17 degrees above normal for the end of February. Warm winds from across the border could bring similar temperatures to the eastern Niagara Peninsula.

Ontario precip Tuesday 7pm

Our first risk for thunderstorms will bubble up on Tuesday as a warm front pulls some instability across southern Ontario. Keep an eye out for passing heavy showers and rumbles of thunder through the afternoon and evening hours.

Thunderstorm risk, then a tremendous cooldown

Things start to change in a hurry once Wednesday rolls around.

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Ontario temp icons Wednesday

Another day of record-breaking warmth is likely across southern and eastern Ontario, with highs likely rising into the teens from Windsor to Ottawa and everyone in between. Watch out for additional rumbles of thunder through the day.

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A dramatic cold front sliding out of northern Ontario will kick off a truly impressive temperature swing heading into Wednesday night. This will be one of the most extreme temperature drops we’ve seen in recent memory, so forecasters will monitor the risk of a flash freeze.

Ontario temps icons Wed PM

Ottawa’s high of 13°C on Wednesday will turn on its head to a brutal low of -13°C by Thursday morning.

Precipitation will quickly change over to snow across southern Ontario as the frigid air takes hold Wednesday night into Thursday. Areas that saw a chance for thunderstorms on Wednesday will see the opportunity for lake-effect snow by Thursday.

This burst of cold won’t last for long. Temperatures will quickly rebound across southern and eastern Ontario heading into next weekend.

Header image courtesy of Pexels.

Stay with The Weather Network for all the latest on your forecast across Ontario.

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