Widespread frost on Tuesday morning in Ontario, wildfire smoke aloft

The week ahead in southern Ontario will feature lots of sunshine, cool and warm temperatures, a little bit of rain, possible frost and even some hazy skies resulting from smoke pushing in from the western U.S. wildfires.

This week will feature an abundant amount of sunshine in southern Ontario, accompanied by shots of cooler and warmer air, some rain, possible frost and even a bit of hazy skies, as a result of the western U.S. wildfire smoke that has pushed in. The good news is that the smoke, which has been blanketing B.C. skies for days, will not have any air quality impacts. Temperatures will be mainly seasonal, aside from a brief warmup with some humidity Wednesday. Details and timing, below.

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  • U.S. wildfire smoke filters into southern Ontario

  • Mid-week warmup with humidity

  • Rain, storms on Wednesday night

  • Keep on top of weather ALERTS in your area


Environment Canada has issued frost advisories across Ontario including parts of the GTA, cottage country, and eastern regions since overnight temperatures will drop to or near 0°C. The agency is urging people to cover up plants as a preventative measure, especially in frost-prone areas.


"Frost advisories are issued when temperatures are expected to reach the freezing mark during the growing season, leading to potential damage and destruction to plants and crops," Environment Canada says.

A warm front will make its way into northern Ontario on Tuesday, but it will stay north of the Nickel Belt region, bringing showers as it treks eastward into Quebec.


Some parts of southern Ontario saw hazy skies on Monday as a result of the western U.S. wildfire smoke that has pushed in. While the wildfire smoke will continue to track across parts of Ontario through September 22, it is expected to remain aloft and no significant air quality impacts are anticipated.


After a cool start to the week, southern Ontario will see a brief warmup for Wednesday, with temperatures expected to reach the mid-20s in many areas. Humidity will also be on the rise, slightly, making it feel closer to 30 across the region.

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The mid-week warmth coming Wednesday will be accompanied by a mostly dry day. However, a strong cold front will slide south into the region in the overnight hours, bringing rain and thunderstorms. The band is expected to weaken as it drops south into Montreal and especially into the GTA.


"Many places south of the 401 [highway] will miss out on significant rain and this is our only significant chance for rain during the next 7-10 days," says The Weather Network meteorologist Dr. Doug Gillham.

Temperatures will drop again Thursday, with cooler temperatures lingering through the weekend. Despite abundant sunshine, it will feel more like early October this weekend. Many places outside of the urban centres will likely see their first frost of the season Saturday morning.

Good news is there will be lots of sunshine and a warming trend for early next week, as a couple days with above seasonal temperatures are possible for mid-week.

Check back as we continue to monitor the weekend forecast.