Canada’s National Weather Forecast – September 20 2026

Tomorrow, September 20, 2026, Canada will begin to feel the first real hints of autumn, and meteorologist Shannon Fernando on The Weather Network broke down what that means for us from coast to coast.

In the west, the Rockies are finally shedding some of that lingering summer heat. Expect daytime highs around 14‑16 °C in Calgary and Edmonton, with a light breeze that feels a bit crisp on the skin. The mountain valleys will stay a touch cooler, dipping down to about 9 °C by evening – perfect for a warm jacket.

Moving eastward, the Prairies get a mixed bag. The southern plains of Saskatchewan and Manitoba will see sunshine early on, but clouds will roll in by mid‑day, bringing a chance of isolated showers – roughly a 30 % probability. Temperatures will hover near 18 °C, a pleasant drop from the July swelter.

Ontario and Quebec will have a more typical early‑fall pattern. Toronto’s highs will sit at a mild 21 °C, while Montreal nudges a few degrees cooler at 19 °C. A few stray showers may pop up in the afternoon, especially around the Great Lakes, but overall it’ll be mostly dry with plenty of sunshine.

The Atlantic provinces, however, will be the rain‑iest. A low‑pressure system moving out of the Gulf of St. Lawrence will drape the region in steady rain, especially in Newfoundland and Nova Scotia. Halifax could see up to 15 mm of rain, with gusty winds reaching 25‑30 km/h. The rain will taper off late in the evening, leaving the ground wet but the sky clearing enough for a few stars to appear.

Up north, the Yukon and Northwest Territories will stay chilly. Yellowknife will be around 5 °C during the day, dropping close to zero at night. Snow isn’t expected yet, but the cold snap could set the stage for early snowfall later this week.

Overall, the national picture is one of transition – a gentle cooling, a few showers in the east, and a steady, comfortable stretch for much of the country. As always, local variations can happen, so it’s wise to keep an eye on your regional forecast before heading out.

Shannon Fernando reminded viewers that while the forecast looks solid, weather is fickle; a sudden storm could still pop up in unexpected places. Stay prepared, grab a light jacket, and enjoy the early‑fall vibes.