Water temperature in Sarnia (ON) in September
Is it warm enough to swim in Sarnia in September? Average water temperature in Sarnia in September is 20.1°C and therefore suitable for comfortable swimming. The warmest water in Sarnia in September is 23.3°C, and the coldest is 16.8°C. Average high air temperature in Sarnia in September is 22°C, and average low temperature is 11°C. To find out the sea temperature today and in the coming days, go to Current sea temperature in Sarnia
Changes water temperature in Sarnia in September 2025, 2024
To get an accurate forecast for the water temperature in Sarnia for any chosen month, compare two years within a 10 year range using the chart below. In addition to the sea water temperature in Sarnia, the selected years in the table also show the values of the maximum and minimum temperatures on each of the days of September.
You can choose any other years:
| Day | 2025 | 2024 | Min | Max |
|---|---|---|---|---|
| 1 September | 19.8°C | 22.4°C | 19.8°C | 22.5°C |
| 2 September | 19.9°C | 21.9°C | 19.9°C | 22.4°C |
| 3 September | 20°C | 21.2°C | 19.7°C | 22.6°C |
| 4 September | 20°C | 21.3°C | 19.4°C | 22.9°C |
| 5 September | 19.6°C | 21.5°C | 19.2°C | 23.3°C |
| 6 September | 21.4°C | 19.2°C | 23°C | |
| 7 September | 20.8°C | 19.1°C | 22.5°C | |
| 8 September | 20.7°C | 19°C | 22.5°C | |
| 9 September | 20.2°C | 18.9°C | 22.5°C | |
| 10 September | 19.9°C | 18.6°C | 22.7°C | |
| 11 September | 19.9°C | 18.7°C | 22.3°C | |
| 12 September | 20.1°C | 18.7°C | 22.2°C | |
| 13 September | 20.4°C | 18.1°C | 21.8°C | |
| 14 September | 20.6°C | 18.1°C | 21.6°C | |
| 15 September | 20.9°C | 18.1°C | 21.3°C |
| Day | 2025 | 2024 | Min | Max |
|---|---|---|---|---|
| 16 September | 20.9°C | 18.1°C | 21.4°C | |
| 17 September | 21°C | 18°C | 21.7°C | |
| 18 September | 21°C | 17.9°C | 21.4°C | |
| 19 September | 20.9°C | 17.7°C | 21.3°C | |
| 20 September | 20.9°C | 17.8°C | 21.1°C | |
| 21 September | 21.1°C | 17.8°C | 21.1°C | |
| 22 September | 21.1°C | 17°C | 21.1°C | |
| 23 September | 20.5°C | 17.2°C | 20.8°C | |
| 24 September | 20.3°C | 17.3°C | 20.9°C | |
| 25 September | 20.4°C | 17.2°C | 21°C | |
| 26 September | 20.1°C | 17.3°C | 21.7°C | |
| 27 September | 20°C | 17°C | 21.6°C | |
| 28 September | 20°C | 16.9°C | 20.5°C | |
| 29 September | 20.4°C | 16.8°C | 20.4°C | |
| 30 September | 19.9°C | 16.8°C | 19.9°C |
Average water temperature in Sarnia in September over a decade
| 2015 | 2016 | 2017 | 2018 | 2019 |
| 20.3°C | 20.9°C | 19.8°C | 20.4°C | 18.9°C |
| 2020 | 2021 | 2022 | 2023 | 2024 |
| 19.8°C | 20.9°C | 21°C | 20.1°C | 20.7°C |
Sarnia sea state in September
Chart comparing the height of waves in Sarnia in September over the past years. The red line indicates the height of the waves when swimming in the sea is prohibited. To view the current sea conditions, click on the graph.
Weather and climate in Sarnia in September
This data display average monthly climate indicators in Sarnia in September based on our historical weather readings over a period of ten years. In addition to temperature, we include data on the number of rainy and sunny days so you can have all the information about your destination before your trip
- Average HIGH temperature22°C
- Average LOW temperature11°C
- Average humidity
91 - Average rainfall days11 days
- Average rainfall4.1''/104mm
- Average sunshine6.4h
Sarnia water temperature during other months:
You can also view information about water temperature for other months by clicking on the month button below
