nomadseason

September Weather in Sarnia, Canada

Last updated: June 18, 2025

In September, the average temperature in Sarnia, Canada is a comfortable 18°C (65°F). You can expect a range from a chilly 5°C (40°F) at night to a warm 33°C (91°F) during the day. It's also a relatively wet month, with 73 mm (2.9 in) of precipitation spread over about 10 days. Don't forget to prepare for the 80% humidity that comes along with the season!

September Temperature in Sarnia

In September in Sarnia, the average temperature is 18°C (65°F). Maximums can reach 33°C (91°F), and minimums can be as low as 5°C (40°F). Be prepared for a range of temperatures, making it ideal for layering your clothing while exploring the area.

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

The chart illustrates September temperature patterns in Sarnia, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Sarnia, September typically has an average temperature of 18°C (65°F), with highs reaching up to 33°C (91°F) and lows dropping to around 5°C (40°F).
JanFebMarAprMayJunJulAugSepOctNovDec262735445668737265544032
Data source: Temperature data for Sarnia 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 Sarnia

In Sarnia in September, the precipitation amount is 73 mm (2.9 in) over the course of 10 days.

September Precipitation Trends in Sarnia

The chart displays monthly precipitation patterns in Sarnia, 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 Sarnia, September typically receives around 73 mm (2.9 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec6166639597867379731067255
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

September Humidity in Sarnia

In Sarnia in September, humidity is 80%. With an average temperature of 18°C (65°F), this humidity feels like wandering through a warm, damp blanket, making every step slightly heavy and resulting in a constant sheen of sweat, which can be both refreshing and exhausting for travelers.

September Average Humidity in Sarnia

This chart illustrates the average monthly humidity levels in Sarnia, 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 Sarnia is approximately 80%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec88%87%85%86%80%80%80%81%80%84%90%86%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Sarnia

In Sarnia 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 Sarnia.

Maximum UV Index Levels in Sarnia for September

The chart shows the monthly maximum UV Index (UVI) for Sarnia 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 Sarnia typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec2458910997532
Data source: Sarnia 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 Sarnia Compares to Other Months

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

This table compares monthly weather conditions in Sarnia, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-3°C (27°F)60 mm (2.4 inches)88%low
February Weather-3°C (28°F)66 mm (2.6 inches)87%moderate
March Weather1°C (35°F)63 mm (2.5 inches)85%moderate
April Weather7°C (45°F)95 mm (3.7 inches)86%very high
May Weather13°C (57°F)97 mm (3.8 inches)80%very high
June Weather20°C (68°F)86 mm (3.4 inches)80%very high
July Weather23°C (73°F)73 mm (2.9 inches)80%very high
August Weather22°C (72°F)79 mm (3.1 inches)80%very high
September Weather18°C (65°F)73 mm (2.9 inches)80%high
October Weather12°C (54°F)106 mm (4.2 inches)84%moderate
November Weather4°C (40°F)72 mm (2.8 inches)89%moderate
December Weather0°C (33°F)55 mm (2.2 inches)86%low

Compare Sarnia's Climate with Cities Worldwide