Ontario to endure wild temperature swing, thunder risk this week

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.

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.

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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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.

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.

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.