The temperatures in Sarnia in September are comfortable with low of 14°C and and high up to 22°C.
You can expect about 3 to 8 days of rain in Sarnia during the month of September. It’s a good idea to bring along your umbrella so that you don’t get caught in poor weather.
Our weather forecast can give you a great sense of what weather to expect in Sarnia in September 2025.
If you’re planning to visit Sarnia in the near future, we highly recommend that you review the 14 day weather forecast for Sarnia before you arrive.
Temperatures
22° / 14°
Rainy Days
6
Snowy Days
0
Dry Days
24
Rainfall
29
mm
Sun Hours
2.3
Hrs
