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Sticky September heat may spawn severe thunderstorms in southern Ontario

The scorching, sticky weather that busted or challenged temperature records across southern Ontario on Tuesday has continued into today, with thunderstorms this afternoon, some potentially severe, heralding the arrival of cooler weather for the rest of the week.

Residents of southern Ontario saw temperatures in the low to mid-30s on Tuesday afternoon, with the humidity making it feel more like it was in the low to mid 40s. One saving grace for yesterday was that there was a fairly consistent wind blowing through the province. It felt more like a hot blast from an oven than a cool breeze, but as this kind of hot and sticky weather is even worse when you add 'stagnant' to the mix, having at least some movement of the air made it a bit more bearable.

[ Related: Much of southern Ontario suffering through sticky September heat ]

The hottest spot in the province was at Sarnia Chris Hadfield Airport, which reached 35.8°C (with a humidex of 41). That beat out the previous record for September 10th, of 34.4°C, set back in 1983. Although it's not official just yet, there were apparently two other big record-breakers: Windsor Airport, which reached 34.6°C (humidex 43), and Toronto Pearson Airport, where it got up to 34.1°C (also with a humidex of 43). The long-standing record for these two cities is from 61 years ago, when both reached a temperature of 33.9°C on September 10th, 1952!

For today, temperatures are still expected to reach into the low 30s across the southern part of the province, and the humidity will still make it feel around ten degrees hotter than that in places. A humidex advisory is still in effect for nearly all of southern Ontario, and cities across the province have continued their alerts and relief measures. Toronto's heat alert remains in effect, as does London's. The City of Hamilton has upgraded their heat advisory to a heat warning, as this is the second day with humidex values of 40 or more. Windsor and Sarnia have declared alerts as well.

This afternoon, things will get a bit more wild, though, as an approaching cold front is expected to stir up this hot, humid weather to produce some thunderstorm activity for the rest of the day and into tonight. There's also the possibility of some severe storms, with torrential downpours and damaging winds, and severe thunderstorm watches are in effect across the southern part of the province.

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Once this little reminder of summer passes, the weather will be cooling down for the rest of the week. Temperatures across the province will only get up into the mid to high teens going into the weekend, and overnight lows will drop down into the single digits. Overall, it should be a fairly mild end to the second last week of summer.

(Photo courtesy: Michelle Siu/The Canadian Press)

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