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Severe thunderstorms, torrential rain possible in Ontario Thursday

Wednesday, July 15th 2020, 8:34 pm - Meteorologists are warning that even non-severe thunderstorms could cause flash flooding on Thursday


Editor's note: This article has been retired. Go HERE for our latest article on the severe weather threat in Ontario on Thursday.


Severe thunderstorms will be possible across many regions in Ontario on Thursday including those in the northwest and in the south. While there will be the occasional rumble of thunder during the morning, thunderstorms will track through with heavy rain and strong winds during the afternoon and evening hours. Some areas are seeing a lower risk for severe thunderstorms than others, but meteorologists are warning that even non-severe thunderstorms can cause flash flooding. Details and timing, below.

Visit our Complete Guide to Summer 2020 for an in-depth look at the Summer Forecast, tips to plan for it and much more


  • Heat surges back on Thursday, feeling well into the 30s, forecasters eyeing widespread risk of severe thunderstorms
  • Hotter still by the weekend through to next week
  • Keep an eye on weather ALERTS in your area


Many regions in Ontario will see unsettled conditions on Thursday as a stateside low pressure system tracks in. Even before its arrival in the evening, a few rumbles of thunder could occur in the southwest, reaching the east by the afternoon hours.

Forecasters are monitoring several areas with the potential for severe storms during the evening hours, particularly around the Golden Horseshoe, but that will depend on a number of factors that haven't become clear yet -- particularly whether the region sees a few hours of sunshine after the day's earlier round of showers.

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"Without sunshine we will just see a second line of showers and possibly a non-severe thunderstorm during the evening and into Thursday night," The Weather Network meteorologist Dr. Doug Gillham says.

"But if the atmosphere has a chance to recover during the afternoon, the other ingredients will be in place for scattered strong to severe thunderstorms with torrential rain and a risk for localized damaging winds and hail."

The Weather Network meteorologist Tyler Hamilton adds that storms in the GTA could mainly be non-severe, but warns that flash flooding is possible due to the risk of heavy downpours.

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Thursday also marks the end of what has been a brief stretch of temperate days in southern Ontario, though the warmup will take a couple of days to get past 30°C.

Many places across the south will still be one or two degrees below that 30°C on Thursday, but with the humidity surging in, that won't be much comfort. Humidex values will feel well above 30, and actually closer to 40 for parts of the southwest and east.


Thursday's surge of temperatures and storm risk will herald the beginning of another hot period, with occasional humidex peaks near 40. Though it is expected to be with us through next week, forecasters say it isn't expected to be quite as intense as the prolonged hot streak that dominated early July.

"However, next week could also bring a stormier pattern with a much higher potential for occasional/passing thunderstorms and much-needed rain – starting Saturday night with additional opportunities through next week," Gillham says.

Stay tuned to The Weather Network as we continue to update the forecast.

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