Rising humidex of near 40 marks muggy start to September in Toronto
Posted September 1, 2026 6:14 am.
Last Updated September 1, 2026 10:40 am.
Toronto stepped into September on Tuesday under thick fog, rising humidity and the risk of scattered showers and thunderstorms.
Environment Canada issued a yellow‑level fog advisory for the city and parts of the eastern GTA , warning of near‑zero visibility in pockets across Toronto, Pickering–Oshawa–Southern Durham, and Vaughan–Richmond Hill–Markham. The advisory has since ended as visibility improved later in the morning.
Mist and fog blanketed much of the region before sunrise, which created challenging conditions for commuters and prompting reminders from Canada’s weather agency to slow down and use headlights. With the fog now lifted, Toronto is expected to see a mix of cloud, sunny breaks and scattered showers, with the risk of thunderstorms developing through the day.
Temperatures are expected to climb to a guaranteed high of 28°C, but the humidex will reach 36, making it feel significantly hotter and marking the beginning of a very muggy stretch.
Conditions remain partly cloudy with a continued risk of thunderstorms, and a warm overnight low of 20°C.
Midweek: Heat, humidity and storm risk
Wednesday brings another round of unsettled weather. Forecasters expect a warm and muggy day with showers and thunderstorms, a high of 28°C, and a humidex pushing 37. Overnight temperatures fall to 18°C, offering little relief from the humidity.
Thursday stays mostly cloudy with a chance of showers or thunderstorms and a high of 26°C. Friday looks calmer and drier, with a mix of sun and cloud and a high near 26°C, offering the first break from the unsettled pattern.
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