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September Weather in St. Catharines, Canada

Last updated: June 18, 2025

In September, the average temperature in St. Catharines, Canada is a pleasant 19°C (66°F), with minimums dipping to 9°C (48°F) and maximums rising to a warm 29°C (85°F). Expect around 69 mm (2.7 in) of precipitation over approximately 9 days, accompanied by an average humidity level of 76%. So, whether you're enjoying sunny afternoons or a refreshing drizzle, be prepared for a variety of weather experiences!

September Temperature in St. Catharines

In September in St. Catharines, the average temperature is 19°C (66°F). Maximum can reach 29°C (85°F) and minimum can be as low as 9°C (48°F). This makes it an ideal time for traveling, offering pleasant weather for outdoor activities and sightseeing.

September Weather in St. Catharines: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in St. Catharines, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In St. Catharines, September typically has an average temperature of 19°C (66°F), with highs reaching up to 29°C (85°F) and lows dropping to around 9°C (48°F).
JanFebMarAprMayJunJulAugSepOctNovDec282935435365737266554234
Data source: Temperature data for St. Catharines generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in St. Catharines

In St. Catharines in September, the precipitation amount is 69 mm (2.7 in) spread over 9 days.

September Precipitation Trends in St. Catharines

The chart displays monthly precipitation patterns in St. Catharines, 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. In St. Catharines, September typically receives around 69 mm (2.7 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec7786711191018210680691268686
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in St. Catharines

In St. Catharines in September, humidity is 76%. With an average temperature of 19°C (66°F), this humidity feels like a warm, thick blanket wrapping around you, making travel mildly uncomfortable and encouraging frequent breaks in shaded or air-conditioned areas.

September Average Humidity in St. Catharines

This chart illustrates the average monthly humidity levels in St. Catharines, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in St. Catharines is approximately 76%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec91%91%88%88%82%80%77%72%76%83%88%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in St. Catharines

In St. Catharines in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in St. Catharines.

Maximum UV Index Levels in St. Catharines for September

The chart shows the monthly maximum UV Index (UVI) for St. Catharines 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. In September, the maximum UV index in St. Catharines typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec2458910997532
Data source: St. Catharines 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.

How September Weather in St. Catharines Compares to Other Months

Weather in St. Catharines varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in St. Catharines, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in St. Catharines, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-2°C (29°F)77 mm (3.0 inches)91%low
February Weather-2°C (29°F)86 mm (3.4 inches)91%moderate
March Weather1°C (35°F)71 mm (2.8 inches)88%moderate
April Weather6°C (43°F)119 mm (4.7 inches)88%very high
May Weather12°C (54°F)101 mm (4.0 inches)82%very high
June Weather18°C (65°F)82 mm (3.2 inches)79%very high
July Weather23°C (73°F)106 mm (4.2 inches)77%very high
August Weather22°C (72°F)80 mm (3.1 inches)72%very high
September Weather19°C (66°F)69 mm (2.7 inches)76%high
October Weather13°C (56°F)126 mm (4.9 inches)83%moderate
November Weather5°C (42°F)86 mm (3.4 inches)88%moderate
December Weather1°C (35°F)86 mm (3.4 inches)87%low

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