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Weather in Sarnia for September 2025

Your guide to Sarnia weather in September - trends and predictions

    Official Weather Alert ⚠️

  • Fog Warning - See hour by hour.

    • Temperatures

  • Until now, September 2025 in Sarnia is cooler than usual, with temperatures averaging 21.2 °C, this is -2.3 °C below the typical seasonal average.

  • The forecast for the next days in Sarnia predicts temperatures to be around 24 °C, close to the historical average.

  • In general, the average temperature in Sarnia at the beginning of September is 23.9 °C. As the month progressed, temperatures tended to moderately fall, reaching an average of 22.7 °C by the end of September.

    • Rain 🌧️

  • Sarnia experiences moderate rainfall in September, with an average of 6 rainy days and a total precipitation of 40.5 mm.

    • More

  • New! Chat with our AI weatherman - it’s amazing and free.

Average dry days
24
Dry days
Average rainy days
6
Rainy days
Average snowy days
0
Snow days
Average temperatures
23°/14°
Temperatures
Average wind speed
19 km/h
Avg max wind
Average humidity
74 %
Avg humidity

Sarnia Weather September

Move between months or click on a day
August
October
Sun.Mon.Tue.Wed.Thu.Fri.Sat.
1
Sunny
23°
2
Overcast
22°
3
Cloudy
27°
4
Partly cloudy
26°
5
Mist
27°
6
Patchy rain possible
23°
7
Light rain shower
19°
8
Patchy rain possible
20°
9
Partly cloudy
23°
10
Overcast
23°
11
Partly cloudy
24°
12
Torrential rain shower
24°
13
Overcast
23°
14
Weather Alert Partly cloudy
24°
15
Fog
20°
16
Fog
23°
17
Sunny
27°
18
Sunny
30°
19
Sunny
27°
20
Patchy rain possible
25°
21
Patchy rain possible
20°
22
Patchy rain possible
18°
23
Partly cloudy
19°
24
Sunny
19°
25
Sunny
25°
26
Sunny
26°
27
Sunny
27°
28
Light rain shower
19°
29
Patchy rain possible
21°
30
Overcast
22°

Temperatures trend during September in Sarnia

See the weather trend as well as the moving average line

September weather in Sarnia day by day

Click on a date for more information
August October
Date Weather Temperatures Rain UV More
1 Sept. Sunny
Sunny
 23° /12° 0 mm 6
2 Sept. Overcast
Overcast
 22° /10° 0 mm 5
3 Sept. Cloudy
Cloudy
 27° /13° 0 mm 6
4 Sept. Partly cloudy
Partly cloudy
 26° /14° 16.4 mm 6
5 Sept. Mist
Mist
 27° /14° 0 mm 6
6 Sept. Patchy rain possible
Patchy rain possible
 23° /13° 4.6 mm 5
7 Sept. Light rain shower
Light rain shower
 19° /12° 2.9 mm 4
8 Sept. Patchy rain possible
Patchy rain possible
 20° /10° 0 mm 5
9 Sept. Partly cloudy
Partly cloudy
 23° /11° 0 mm 6
10 Sept. Overcast
Overcast
 23° /13° 0 mm 5
11 Sept. Partly cloudy
Partly cloudy
 24° /14° 0.3 mm 6
12 Sept. Torrential rain shower
Torrential rain shower
 24° /14° 9.1 mm 5
13 Sept. Overcast
Overcast
 23° /12° 0 mm 6
14 Sept. Partly cloudy
Partly cloudy
 24° /13° 0 mm 1.4
15 Sept. Fog
Fog
 20° /15° 0 mm 1.4
16 Sept. Fog
Fog
 23° /16° 0 mm 1.4
17 Sept. Sunny
Sunny
 27° /15° 0 mm 1.4
18 Sept. Sunny
Sunny
 30° /17° 0 mm 0
19 Sept. Sunny
Sunny
 27° /18° 0 mm 6
20 Sept. Patchy rain possible
Patchy rain possible
 25° /16° 0.4 mm 5
21 Sept. Patchy rain possible
Patchy rain possible
 20° /17° 1.6 mm 4
22 Sept. Patchy rain possible
Patchy rain possible
 18° /12° 0.1 mm 3
23 Sept. Partly cloudy
Partly cloudy
 19° /10° 0 mm 4
24 Sept. Sunny
Sunny
 19° /13° 0 mm 5
25 Sept. Sunny
Sunny
 25° /11° 0 mm 5
26 Sept. Sunny
Sunny
 26° /15° 0 mm 5
27 Sept. Sunny
Sunny
 27° /16° 0 mm 6
28 Sept. Light rain shower
Light rain shower
 19° /15° 1.4 mm 4
29 Sept. Patchy rain possible
Patchy rain possible
 21° /15° 0.2 mm 5
30 Sept. Overcast
Overcast
 22° /15° 0 mm 5
Next
Important Notice
Our weather forecast for Sarnia in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the Sarnia forecast closer to your planned date for the most up-to-date weather information.
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Sarnia in September - FAQ

What are the expected maximum and minimum temperatures in Sarnia during September?
Enjoy moderate daytime temperatures of up to 23° and cooler nights around 14°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Sarnia during September?
In September, Sarnia can expect light to moderate rainfall, totaling 40.5 mm across approximately 6 days. Occasional showers are possible, and planning ahead for them could be helpful.
What are the typical wind conditions in Sarnia during September?
The average wind speed in Sarnia during September is 19 km/h, suggesting breezy to windy conditions, depending on your activities.

September rainfall patterns in Sarnia

Explore the daily rainfall trends and prepare for Sarnias September weather 💧

UV exposure in Sarnia during September

Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️

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Get accurate weather forecasts for Sarnia, located at latitude 42.979 and longitude -82.404. Stay updated with localized weather information tailored for Sarnia.

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