Montréal weather in September
In September, Montréal has an average high of 21 °C70 °F and an average low of 10 °C50 °F, with about 88 mm3.5 in of precipitation. It is the 4th warmest month of the year and ranks 8th for precipitation.
How September compares with other months
Compared with August, September is 4.2 °C7.6 °F cooler on average and drier by 10 mm0.4 in. Compared with October, September is 8 °C14.5 °F warmer on average and drier by 26 mm1.0 in. Daylight lasts about 12.5 hours around the middle of the month. Average relative humidity is 75% and the average cloud amount 54%.
Is September a good time to visit Montréal?
Yes — September is one of the most comfortable months to visit Montréal by our comfort score, which favours average highs of 21–28 °C, lows above 5 °C, little rain and moderate humidity.
What to wear in September
For Montréal in September, pack light layers — T-shirts plus a light sweater or jacket and an extra layer for the cooler mornings and evenings.
September in nearby places
| Place | High °C°F | Low °C°F | Precip. mmin |
|---|---|---|---|
| Montréal | 2170 | 1050 | 883.5 |
| Trois-Rivières | 2069 | 1050 | 923.6 |
| Sherbrooke | 2069 | 1050 | 923.6 |
| Ottawa | 2271 | 1051 | 873.4 |
| Québec | 2067 | 1050 | 1094.3 |
| Kingston | 2170 | 1559 | 783.1 |
| Albany | 2576 | 1254 | 1094.3 |
| Manchester | 2374 | 1253 | 903.5 |
| Syracuse | 2475 | 1355 | 973.8 |
Nearby places that are more than 1 °C1.8 °F warmer in September: Kingston, Albany, Manchester and Syracuse.
Other months in Montréal
- January−7 °C19 °F / −18 °C0 °F
- February−5 °C23 °F / −16 °C3 °F
- March0 °C33 °F / −9 °C15 °F
- April9 °C49 °F / −1 °C31 °F
- May17 °C63 °F / 7 °C44 °F
- June22 °C72 °F / 13 °C55 °F
- July25 °C78 °F / 16 °C60 °F
- August25 °C77 °F / 15 °C59 °F
- September21 °C70 °F / 10 °C50 °F
- October12 °C54 °F / 3 °C38 °F
- November4 °C39 °F / −4 °C26 °F
- December−4 °C26 °F / −12 °C10 °F
Frequently asked questions
How warm is Montréal in September?
In September the average high in Montréal is 21 °C (70 °F) and the average low is 10 °C (50 °F).
Does it rain a lot in Montréal in September?
On average about 88 mm (3.5 in) of precipitation falls in September; it ranks 8th of the 12 months.
Is September the warmest month in Montréal?
No. The warmest month in Montréal is July, with an average high of 25 °C (78 °F). The coldest month is January, with an average low of -18 °C (0 °F).
How long is the day in Montréal in September?
In the middle of September the day in Montréal lasts about 12.5 hours from sunrise to sunset. The value is calculated from the position of the city and the sun.
How humid is Montréal in September?
The average relative humidity in September is about 75%. This is a long-term average for the whole day.
How cloudy is Montréal in September?
On average about 54% of the sky is covered by cloud in September. This is the mean cloud amount from satellite data, not the number of sunny days.
About this data
All figures are 25-year averages (January 2001 – December 2025) from the NASA POWER project. Temperature, humidity, wind and precipitation come from the MERRA-2 reanalysis (precipitation is the bias-corrected MERRA-2 product), cloud and solar values from CERES satellite data. They describe a grid cell of roughly 50–70 km, not a single weather station, so they can differ from airport records — most of all on coasts, in mountains and for rainfall. Average highs and lows are the monthly mean temperature plus/minus half of the average daily temperature range. Counts of rainy days are not part of this dataset.
The grid cell’s average elevation is 38 m, while Montréal lies at about 216 m. Temperatures on this page were therefore adjusted by −1.2 °C2.1 °F using the standard lapse rate of 6.5 °C per 1,000 m.