Fall chill brings snow, risk for waterspouts, storms in Ontario

Thursday will be unsettled in Ontario once again, with possible lake-effect showers for the south, a chance of waterspouts for Lake Huron and Erie and snow in the north.

Wednesday saw some stormy conditions in southern Ontario, with thunderstorms dropping small hail, waterspouts and strong winds, which damaged a farm property in rural Hamilton. It is being investigated as a possible tornado. The unsettled, cool conditions will continue in Ontario Thursday, with the chance for more waterspouts, lake-effect showers, thunderstorms and even snow in parts of the northern regions. Friday will see similar conditions, thanks to the upper level trough in place. Details and timing, below.


  • Lake-effect showers, thunderstorm risk in southern Ontario on Thursday

  • Elevated chance of waterspouts in Lake Huron and Lake Erie

  • Cooler air triggers snow in the north; further temperature drop on the weekend in the south


Isolated, lake-effect showers will continue in southern Ontario Thursday afternoon, thanks to a short wave trough moving through. There is even the potential for non-severe thunderstorms due to cool, unstable air in the upper levels of the atmosphere.

More waterspouts are also possible lakes Ontario and Erie, as the cold air aloft will hang over the warmer waters of the Great Lakes and a lingering trough providing instability. Wednesday saw 29 confirmed.


Daytime highs will sit close to or slightly-below seasonal for southern Ontario, a sharp contrast to the temperatures in the mid-20s at the beginning of the week. The cooldown will continue through the weekend, with temperatures falling even more.

Westerly winds will be gusty at times, reaching 30-40 km/h through the evening before easing overnight.


Meanwhile, several northern regions will see some October snowfall. For most, it'll be no more than short-lived "conversational" snow, and not at all out of the ordinary for early October, but still a reminder that summer is definitely over.

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Friday will be somewhat unsettled still in southern Ontario, thanks the the trough hanging over the Great Lakes region. However, the showers will be quite light and more isolated and pop-up in nature.

Temperatures will drop even further, with daytime highs a few degrees below seasonal.

On the weekend, southern Ontario can expect the coldest weather of the season thus far with temperatures more typical of late October. Mostly cloudy skies and peeks of sun are expected Saturday with a low risk for a passing shower. Rain will develop from west to east across the region on Sunday.

ON Sat Temp

Beyond, a brief warming trend back to seasonal during the first half of next week, but a system is expected to track across the region around Wednesday, with rain followed by another shot of cold air for the end of the week – this could be the coldest air of the season thus far, especially for eastern Ontario.

Temperatures will quickly rebound during the long weekend, but forecasters are watching the potential for one more cold front to track across the region during. The models are split on whether there will be another shot of cool weather before a more extended period of mild weather arrives for the following week (mid-October) or if the cooler weather stays to the north – allowing the warmup to continue through the long weekend.

Check back for updates as we continue to monitor the late week forecast