Toronto weather in September

Toronto's September is a forum favourite: still warm but past the humid stretch, with a monthly high near 21°C easing to about 15 overnight and a hint of autumn in the evenings. Regulars split the month in two — early September is pleasant and quieter once children are back in school, while late September turns cool, crisp and often sunny. The one thing to plan around is cost rather than climate: the Toronto International Film Festival runs through the first half of the month and pushes hotel prices up.

Regulars describe this as commonly hot, hazy and humid, with the humidex figure occasionally pushing into the high 30s or even 40s Celsius - though regulars are specific this extreme happens maybe half a dozen times a year and rarely lasts more than three or four days at a stretch. Our row backs the real heat and humidity, 27.6C reading as a hot 29C at 72 percent humidity, over 18.4C nights, with 83.9mm of rain across 8.4 days. Regulars are candid that a genuinely oppressive multi-week humid stretch does happen most summers, serious enough that the city opens cooling centres, and recommend an air-conditioned room as a real priority rather than a nice-to-have for anyone sensitive to the heat. The record: 12.1 hours of sun, a 16.4 kph wind and AQI 70.

May here swings well outside its own averages, and regulars describe the daily pattern rather than a single number: cool mornings and evenings, warm to hot afternoons, and a genuinely cold turn whenever the wind picks up, which is Lake Ontario's spring cooling effect at work. Our row backs that variability at 19C over 9.6C, with 67mm of rain across 9.2 days. Patios and rooftops are a live question early in the month - most have heaters, but some places wait for reliably warmer weeks before opening fully. Swimming is not on the table yet even at month's end; the lake itself stays too cold. Layers, including a rainproof one, is the standing packing advice. The record: humidity 73 percent, 10.6 hours of sun, an 18.2 kph wind and AQI 69.

Regulars here blame the lake and they are right to: moisture off Ontario gives the city two or three weeks of heavy humidity most summers, enough for official warnings and cooling centres. August carries it, though they note July is usually the hotter month and that late August nights are noticeably cooler. Our row gives 26.5C reading as 28C over 17.8C nights at 73 percent humidity and a 14.9C dew point, which is the sticky part quantified. Thunderstorms are commoner this month and they break it for a day. Rain totals 67.5mm across 6.3 days. The Ex runs through the end of the month on the waterfront. The record: 11.3 hours of sun and AQI 55.

Toronto-forum threads on June weather describe a month that's warm and mostly sunny without yet being oppressive: highs in the low-to-mid 20s, humidity that only really bites above 25C and rarely for long stretches this early in summer, and posters call out neighbourhood festivals hitting full swing alongside the last of spring's foliage. Rain is called a little above average for the year rather than a defining feature. June's record: 24.5C days feeling like 25C, 14.9C nights, 70mm of rain across 9.1 days, 12 hours of sun - warm t-shirt weather with a light jacket worth keeping in the bag for evenings. One thing the forums don't dwell on: AQI runs 79 here, on the higher side for a North American summer month.