Potent cold front to spark strong storms in Ontario, autumnal chill follows

A cold front associated with an unusually strong upper low is expected to sweep across southern Ontario Thursday, bringing a line of thunderstorms and strong wind gusts through the evening and overnight hours.

Heavy rain and nickel-sized hail are other risks with these storms, as the system continues to make its way eastwards ahead of the weekend.

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There will be a hint of autumn in the air, with rather cool temperatures and a brisk northwest wind behind the cold front. High temperatures will only reach the mid to upper teens on Friday across much of cottage country.

Thursday through Friday

Areas: Much of Ontario

Timing: Late afternoon Thursday through the overnight

Weather: A strong low pressure that moved through northwestern Ontario on Wednesday is bringing with it a cold front that will sweep into southern Ontario Thursday. This cold front will bring a line of thunderstorms with heavy rain and strong wind gusts, and potentially even some nickel-sized hail.

While much of northeastern and southern Ontario will see the storm risk through the late afternoon and early evening hours, the deteriorating conditions won't occur for eastern Ontario until the overnight hours on Thursday and into Friday.

This system will bring a widespread rain for many areas, but the highest accumulations will be across eastern Ontario, where nocturnal storms could bring the threat for some localized flooding.

The low will slowly move out of the area late Friday, though with scattered rain and a cool northerly breeze continuing.

What will be most notable with this system is how strong the winds will be both Thursday and Friday. Wind gusts will be widespread and persistent, and could exceed 60 km/h on both days.

Prepare

Make sure to keep up-to-date on your local forecast information and alerts. If you are outdoors in an area with a severe weather threat, make sure you have a safety plan in place in case you need to get to shelter.

If a severe thunderstorm approaches your location, remain mindful of trees or tree limbs that loom near your home. Trees falling into buildings are a significant source of injury during strong storms. Try to avoid rooms where trees may cause damage during high winds.

The greatest danger in any thunderstorm is lightning. If you can hear thunder, you’re close enough to be struck by lightning.

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Be sure to check back for the latest weather updates across Ontario.