September Weather in Montreal, Canada

Last updated: April 22, 2025

In September, Montreal experiences a dynamic blend of warm days and cool nights, with temperatures reaching a maximum of 32°C (90°F) and dipping to a minimum of 2°C (35°F). The average temperature settles around 16°C (62°F), providing a comfortable backdrop for outdoor activities. This month also witnesses 73 mm (2.9 in) of precipitation over 9 days, contributing to a humidity level of 78%. As summer fades and autumn approaches, the city's vibrant atmosphere is complemented by a refreshing mix of sunshine and intermittent showers.

September Temperature in Montreal

As summer gracefully transitions into fall, September in Montreal witnesses a delightful shift in temperatures. The month begins with a refreshing chill, with nighttime lows dipping to around 2°C (35°F), while the average daytime warmth settles at a comfortable 16°C (62°F). Those golden September days can still bring delightful warmth, with highs reaching up to 32°C (90°F), providing a picturesque backdrop for outdoor activities. This fluctuation not only highlights the lingering summer vibes but also hints at the impending cooler weather. As leaves start to change color and fall begins to creep in, September offers a unique blend of warmth and crispness that captures the essence of Montreal's dynamic climate.

September Weather in Montreal: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Montreal, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends.
JanFebMarAprMayJunJulAugSepOctNovDec171929435766727062503524
Data source: Temperature data for Montreal generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Montreal

In September, Montreal experiences a notable shift in its precipitation patterns, with a total of 73 mm (2.9 in) of rain falling over just 9 days. This marks a decrease compared to the preceding summer months, where rainfall was more abundant, particularly in July and August, which both exceeded 100 mm. As the city transitions into fall, September delivers milder precipitation, setting the stage for the wetter October ahead, which averages 139 mm (5.5 in). This trend of decreasing precipitation in September, contrasted with the uptick expected in October, reflects the seasonal progression in Montreal, where the crisp air and changing leaves hint at the impending winter months.

September Precipitation Trends in Montreal

The chart displays monthly precipitation patterns in Montreal, with values for each month alongside September's data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September's conditions compare to those of other months.
JanFebMarAprMayJunJulAugSepOctNovDec848284121971041031097313911888
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

September Humidity in Montreal

In September, Montreal experiences a relative humidity of 78%, marking a slight uptick from the summer months of July and August, which sit at 76% and 75%, respectively. As the city transitions into autumn, humidity levels resurge, echoing the gradual increase experienced from May's more comfortable 80%. This uptick signals the approaching cooler months, where humidity will continue to climb, reaching 86% in October. Overall, September stands as a transitional month, balancing the lingering warmth of summer with the onset of the more humid conditions characteristic of fall in Montreal.

September Average Humidity in Montreal

This chart illustrates the average monthly humidity levels in Montreal, with September's data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, allowing you to see how September's humidity levels compare to other months.
JanFebMarAprMayJunJulAugSepOctNovDec93%92%86%85%80%74%76%75%78%86%89%89%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Montreal

As September rolls into Montreal, the UV Index makes a notable transition to 7, falling into the high exposure category, indicating a shift from the peak summer months. While this is a decrease from the intense summer readings of 8-9, it still suggests that residents and visitors should exercise caution. With a burn time of 25 minutes, it's essential to be sun-smart during outdoor activities. This month signals the start of autumn, but UV radiation remains significant. As temperatures cool, don’t forget to check the UV Index regularly for safe sun exposure guidelines. For more detailed insights, visit Montreal UV Index.

Maximum UV Index Levels in Montreal for September

The chart shows the monthly maximum UV Index (UVI) for Montreal in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues.
JanFebMarAprMayJunJulAugSepOctNovDec245799887532
Data source: Montreal September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

September Sunshine in Montreal

September in Montreal marks the gentle transition from summer to autumn, boasting 281 hours of sunshine that invite locals and visitors alike to embrace the outdoors. After the vivacious heat of July, which shines for an impressive 342 hours, the city begins to cool, yet still retains a comforting warmth. August sees a slight dip to 326 hours, and as September rolls in, sunshine continues to grace the city, contributing to its vibrant atmosphere. This month strikes a perfect balance—warm days ideal for exploring parks and festivals, coupled with the breathtaking fall foliage that begins to emerge. As daylight shortens heading into October, where sunshine dwindles to 196 hours, September serves as a beautiful farewell to summer, encouraging a final burst of activity before the chill sets in.

Monthly Sunshine Duration in Montreal: September Highlighted

The September sunshine duration represents the total number of hours Montreal experiences direct sunlight during the month of September, excluding cloudy or obstructed periods. This chart compares the sunshine duration of September with the other months of the year.
JanFebMarAprMayJunJulAugSepOctNovDec118h155h236h226h285h321h342h326h281h196h146h143h
Data source: Montreal September Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Montreal During September

As September rolls in, Montrealers can expect a 41% chance of sunny weather, marking a delightful transition from the summer's warm embrace. Interestingly, this month follows August's sunnier disposition, which boasts a 45% chance, suggesting that the post-summer vibe can still bring plenty of bright days. Compared to the earlier months of the year, September's likelihood of sunshine is noticeably higher than the dreary winter months, such as January and February, which hover around 37% and 39%, respectively. This trend highlights September as a noteworthy month for outdoor activities, offering a charming balance between lingering summer warmth and the onset of autumn's crispness.

Percentage of Sunny Days in September in Montreal

The chart illustrates the percentage of sunny days in Montreal throughout the year, with September highlighted. It highlights the variation in sunshine across each month and provides an overview of the typical frequency of sunny days, offering insights into how often Montreal experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec37%39%43%36%41%36%33%46%41%29%45%29%
Data source: Montreal September chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Montreal in September

As summer gives way to fall, September in Montreal experiences a charming shift in daylight duration, offering about 12 hours of sunlight each day. This marks a gentle decline from the 14 hours enjoyed in August, signaling the onset of autumn. The gradual shortening of days reflects a broader seasonal trend, where daylight peaks in the heights of summer with 15 hours in June and July, before ebbing downwards through the autumn months. This transition brings cooler temperatures and colorful foliage, creating a picturesque backdrop for outdoor activities as the city prepares for the cozy embrace of winter.

Average Daylight Hours in Montreal for September

The chart illustrates the variation in daylight duration in Montreal throughout the year, with September highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec9h 8m10h 23m11h 57m13h 33m14h 55m15h 36m15h 14m14h12h 28m10h 52m9h 28m8h 45m
Data source: Montreal daylight hours, calculated by summing the hours between sunrise and sunset for each day.

September Winds in Montreal

As September arrives in Montreal, the city's atmosphere begins to shift subtly, marked by an average wind speed of 3.4 m/s (8 mph). This gentle breeze echoes the transition from summer's warmth to the crisp anticipation of autumn. Interestingly, September's wind speed remains consistent with the preceding months of May and June, but noticeably softer than the more vigorous gusts of March, which saw an average of 4.5 m/s (10 mph). With the change in seasons, the breezy September air carries a hint of impending coolness, reminding locals of the vibrant foliage and fresh pumpkin spice that are just around the corner.

Average September Wind Speed in Montreal

The chart displays monthly wind speed patterns in Montreal, with values for each month shown alongside September's data, which is highlighted for easy comparison. It illustrates the average wind speed, offering insights into how September's wind conditions compare to the rest of the year.
JanFebMarAprMayJunJulAugSepOctNovDec3.23.64.53.53.43.73.03.03.4 m/s3.23.44.0
Data source: Montreal September wind data, generated using information from the Copernicus Climate Change Service.

How September Weather in Montreal Compares to Other Months

The weather in Montreal changes throughout the year, offering a unique experience in each season. Below is a month-by-month comparison of September's weather with other months, highlighting differences in temperature, precipitation, and other key factors. Click on each section to discover seasonal trends in Montreal and find detailed weather information for every month.

September and January present strikingly contrasting weather conditions. In September, the temperatures range from a mild 2°C (35°F) to a warm 32°C (90°F), with an average of 16°C (62°F). This month sees about 73 mm (2.9 in) of precipitation over approximately 9 days, accompanied by a humidity level of 78%. In stark contrast, January features much harsher weather, with temperatures plummeting to a minimum of -32°C (-25°F) and peaking at just 9°C (49°F), averaging -8°C (17°F). The month experiences a bit more precipitation at 84 mm (3.3 in) over 11 days, but the humidity is notably higher at 93%. To learn more about Montreal's January conditions, visit Montreal weather in January.

When comparing September and February weather, notable differences emerge in temperature and precipitation patterns. In September, temperatures range from a chilly 2°C (35°F) at night to a warm 32°C (90°F) during the day, contributing to an average of 16°C (62°F). The month typically sees about 73 mm (2.9 inches) of rainfall over approximately 9 days, coupled with a humidity level of 78%. In stark contrast, February presents a much harsher climate, with temperatures dropping to a minimum of -25°C (-13°F) and peaking at 13°C (56°F), resulting in an average temperature of -7°C (20°F). This winter month experiences slightly more precipitation at 82 mm (3.2 inches) spread over 12 days, with a higher humidity level of 92%. For more detailed insights into February's weather conditions, you can refer to Montreal weather in February.

In comparing the weather of September and March, one can observe stark contrasts. September typically experiences milder temperatures, ranging from a minimum of 2°C (35°F) to a warm average of 16°C (62°F), peaking at 32°C (90°F). However, it also sees a fair amount of precipitation, with 73 mm (2.9 in) over about 9 days and a humidity level of 78%.

In contrast, March presents a much chillier scenario, where temperatures can plunge to a minimum of -23°C (-9°F), with an average of -2°C (29°F) and a maximum of 20°C (69°F). Although precipitation is slightly higher at 84 mm (3.3 in) over 11 days, the humidity is notably higher at 86%.

For a more detailed understanding of March's conditions, you can visit Montreal weather in March.

September and April present contrasting weather conditions, showcasing the transitional nature of the seasons. In September, temperatures range from a low of 2°C (35°F) to a high of 32°C (90°F), with an average of 16°C (62°F), while April experiences cooler temperatures, with a minimum of -10°C (14°F), an average of 6°C (43°F), and a maximum of 25°C (78°F). Both months see significant precipitation, with September receiving 73 mm (2.9 in) over 9 days and April having 121 mm (4.7 in) across 12 days. Additionally, humidity levels are relatively high, with April reaching 85% compared to September's 78%. For more details, you can check Montreal weather in April.

September and May offer distinct weather patterns, showcasing the transition between seasons. In September, temperatures range from a chilly 2°C (35°F) at night to a warm average of 16°C (62°F), reaching a maximum of 32°C (90°F) during the day. The month experiences about 73 mm (2.9 in) of precipitation over 9 days, with a humidity level of 78%. In contrast, May presents cooler nights with temperatures dropping to -1°C (30°F) and an average of 14°C (57°F), boasting a higher maximum of 36°C (97°F). Precipitation is slightly higher at 97 mm (3.8 in) over 11 days, with humidity at 80%. To learn more about the weather patterns typical for this time of year, check Montreal weather in May.

In September, the weather features a broader temperature range with minimums dipping to 2°C (35°F) and maximums reaching up to 32°C (90°F), yielding an average temperature of 16°C (62°F). Contrastingly, June boasts slightly higher temperatures, with a minimum of 3°C (38°F) and a maximum of 34°C (94°F), leading to a higher average of 19°C (67°F). Rainfall is also more pronounced in June, with 103 mm (4.1 in) falling over 12 days, compared to September's 73 mm (2.9 in) spread over 9 days. However, humidity levels are slightly higher in September at 78%, compared to June's 74%. For more information about the weather specifics in June, check the link: Montreal weather in June.

In comparison to July, September shows a noticeable drop in temperature, with a minimum of 2°C (35°F) versus July's 10°C (50°F), and an average temperature of 16°C (62°F) compared to July's warmer 22°C (72°F). The maximum temperature in September reaches up to 32°C (90°F), while July peaks at a higher 35°C (95°F). Precipitation is also more frequent in July, recorded at 103 mm (4.1 in) over 14 days, compared to September's 73 mm (2.9 in) over 9 days. Humidity levels are fairly similar, with September at 78% and July slightly lower at 76%. For more details, visit Montreal weather in July.

In comparing the weather between August and September, September generally presents a more varied temperature range, with minimums dipping to 2°C (35°F) and maximums reaching up to 32°C (90°F), while August features milder lows of 8°C (47°F) and slightly higher highs at 33°C (92°F). The average temperature in September is cooler at 16°C (62°F) compared to August's average of 21°C (70°F). Additionally, September experiences less precipitation, with 73 mm (2.9 in) over 9 days compared to August's 109 mm (4.3 in) across 13 days, while September's humidity levels are slightly higher at 78% versus August's 75%. For those interested in detailed weather patterns, you can find more information Montreal weather in August.

September offers a warm transition into fall, with average temperatures around 16°C (62°F) and maximums that can reach up to 32°C (90°F). However, as we move into October, the weather takes a noticeable turn towards cooler conditions, with average temperatures dropping to 10°C (50°F) and a minimum that can plummet to -4°C (25°F). Additionally, October is characterized by higher precipitation levels, with 139 mm (5.5 in) over 13 days, compared to September's 73 mm (2.9 in) over 9 days. Humidity also increases slightly, reaching 86% in October from September's 78%. For more detailed insights, you can check Montreal weather in October.

September in Montreal typically features a significant range in temperatures, with lows around 2°C (35°F) and highs reaching up to 32°C (90°F), and an average of 16°C (62°F). The month experiences moderate precipitation, with about 73 mm (2.9 in) over approximately 9 days, resulting in a humidity level of 78%. In contrast, November sees much colder conditions, with temperatures dropping to a minimum of -17°C (1°F) and an average of 2°C (35°F), while highs peak at 23°C (73°F). Precipitation increases to 118 mm (4.6 in) over 13 days, accompanied by a higher humidity level of 88%. For more detailed insights on November weather in Montreal, check Montreal weather in November.

In September, temperatures range between a minimum of 2°C (35°F) and a maximum of 32°C (90°F), averaging around 16°C (62°F). This month experiences relatively mild weather with an average humidity of 78% and approximately 73 mm (2.9 in) of precipitation over 9 days.

Conversely, December brings a stark contrast with frigid temperatures that can dip as low as -26°C (-15°F) and peak at 14°C (57°F), averaging around -5°C (24°F). The month is characterized by higher precipitation, totaling about 88 mm (3.5 in) over 12 days, and increased humidity at 89%. For more details on the winter climate, check Montreal weather in December.

Compare Montreal's Climate with Cities Worldwide

Conclusion: What to Expect From September Weather in Montreal

As summer transitions to fall, September in Montreal offers a unique blend of weather that sets it apart from the rest of the year. With temperatures dipping from the highs of summer yet still reaching a pleasant warmth, the month boasts a comfortable average that invites outdoor activities. However, it also marks a rise in precipitation, with more frequent rainy days than in the drier summer months, leaving a refreshing yet humid atmosphere. This change not only transforms the scenery into vibrant autumn hues but also prepares the city for the cooler days ahead. For a deeper look into the patterns and nuances of Montreal's climate, be sure to check out Montreal Climate.