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Weather in Thunder Bay for September 2025

Your guide to Thunder Bay weather in September - trends and predictions

    Temperatures

  • Until now, September 2025 in Thunder Bay is cooler than usual, with temperatures averaging 15.3 °C, this is -4 °C below the typical seasonal average.

  • The forecast for the next days in Thunder Bay predicts temperatures to be around 20 °C, close to the historical average.

  • In general, the average temperature in Thunder Bay at the beginning of September is 20.3 °C. As the month progressed, temperatures tended to moderately rise, reaching an average of 21.9 °C by the end of September.

    • Rain 🌧️

  • Thunder Bay experiences moderate rainfall in September, with an average of 9 rainy days and a total precipitation of 58.2 mm.

    • More

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Average dry days
21
Dry days
Average rainy days
9
Rainy days
Average snowy days
0
Snow days
Average temperatures
20°/11°
Temperatures
Average wind speed
15 km/h
Avg max wind
Average humidity
77 %
Avg humidity

Thunder Bay Weather September

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

Temperatures trend during September in Thunder Bay

See the weather trend as well as the moving average line

September weather in Thunder Bay day by day

Click on a date for more information
August October
Date Weather Temperatures Rain UV More
1 Sept. Patchy rain possible
Patchy rain possible
 21° /11° 0 mm 5
2 Sept. Sunny
Sunny
 25° /12° 4.2 mm 6
3 Sept. Partly cloudy
Partly cloudy
 23° /10° 16.9 mm 5
4 Sept. Partly cloudy
Partly cloudy
 20° /11° 1.4 mm 5
5 Sept. Fog
Fog
 19° /10° 4.2 mm 4
6 Sept. Light rain shower
Light rain shower
 16° /6° 11 mm 4
7 Sept. Partly cloudy
Partly cloudy
 18° /6° 0 mm 5
8 Sept. Mist
Mist
 19° /6° 3.6 mm 4
9 Sept. Light drizzle
Light drizzle
 18° /10° 10 mm 5
10 Sept. Light rain shower
Light rain shower
 19° /11° 1 mm 5
11 Sept. Overcast
Overcast
 18° /10° 0 mm 4
12 Sept. Overcast
Overcast
 16° /9° 0 mm 4
13 Sept. Sunny
Sunny
 20° /10° 0 mm 5
14 Sept. Fog
Fog
 15° /12° 0 mm 1.2
15 Sept. Fog
Fog
 19° /11° 0 mm 1.2
16 Sept. Mist
Mist
 23° /13° 0 mm 1.1
17 Sept. Patchy rain possible
Patchy rain possible
 22° /15° 4.3 mm 1
18 Sept. Sunny
Sunny
 17° /11° 0 mm 0
19 Sept. Partly cloudy
Partly cloudy
 13° /10° 0 mm 4
20 Sept. Patchy rain possible
Patchy rain possible
 11° /10° 1.3 mm 3
21 Sept. Cloudy
Cloudy
 19° /10° 0.1 mm 3
22 Sept. Sunny
Sunny
 19° /8° 0 mm 4
23 Sept. Sunny
Sunny
 22° /10° 0 mm 5
24 Sept. Sunny
Sunny
 22° /12° 0 mm 5
25 Sept. Sunny
Sunny
 25° /13° 0 mm 5
26 Sept. Sunny
Sunny
 25° /15° 0 mm 5
27 Sept. Partly cloudy
Partly cloudy
 22° /16° 0.1 mm 5
28 Sept. Mist
Mist
 20° /10° 0 mm 5
29 Sept. Fog
Fog
 19° /11° 0.9 mm 5
30 Sept. Light rain shower
Light rain shower
 20° /9° 1.7 mm 5
Next
Important Notice
Our weather forecast for Thunder Bay 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 Thunder Bay forecast closer to your planned date for the most up-to-date weather information.
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Thunder Bay in September - FAQ

What are the expected maximum and minimum temperatures in Thunder Bay during September?
Enjoy moderate daytime temperatures of up to 20° and cooler nights around 11°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Thunder Bay during September?
Moderate rainfall is anticipated in Thunder Bay during September, with a total of 58.2 mm spread over approximately 9 days. Considering plans for rainy days is advisable.
What are the typical wind conditions in Thunder Bay during September?
The average wind speed in Thunder Bay during September is 15 km/h, suggesting breezy to windy conditions, depending on your activities.

September rainfall patterns in Thunder Bay

Explore the daily rainfall trends and prepare for Thunder Bays September weather 💧

UV exposure in Thunder Bay during September

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

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Location coordinates Where is Thunder Bay?

Get accurate weather forecasts for Thunder Bay, located at latitude 48.382 and longitude -89.25. Stay updated with localized weather information tailored for Thunder Bay.

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