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Weather in Thunder Bay for September 2026

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

    Temperatures

  • So far, September 2026 in Thunder Bay shows a warmer trend than usual by 2.5 °C.

  • Expect cooler weather in the next days in Thunder Bay with the forecast suggesting a temperature of 17.2 °C, lower than the historical average.

  • In general, the average temperature in Thunder Bay at the beginning of September is 21.1 °C. As the month progressed, temperatures tended to moderately fall, reaching an average of 19.6 °C by the end of September.

    • Rain 🌧️

  • The climate of Thunder Bay in September is notably wet, with an average of 15 rainy days, and a total of 113.7 mm of precipitation.

    • More

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Average dry days
15
Dry days
Average rainy days
15
Rainy days
Average snowy days
0
Snow days
Average temperatures
19°/11°
Temperatures
Average wind speed
15 km/h
Avg max wind
Average humidity
79 %
Avg humidity

Thunder Bay Weather September

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

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. Sunny
Sunny
 24° /12° 0 mm 5
2 Sept. Sunny
Sunny
 25° /12° 3.2 mm 6
3 Sept. Partly cloudy
Partly cloudy
 23° /10° 12.6 mm 5
4 Sept. Partly cloudy
Partly cloudy
 19° /12° 6.7 mm 4
5 Sept. Fog
Fog
 20° /10° 3.1 mm 5
6 Sept. Light rain shower
Light rain shower
 19° /7° 8.3 mm 4
7 Sept. Partly cloudy
Partly cloudy
 18° /8° 0.4 mm 4
8 Sept. Mist
Mist
 20° /9° 30.9 mm 4
9 Sept. Light drizzle
Light drizzle
 18° /11° 7.6 mm 5
10 Sept. Sunny
Sunny
 24° /8° 0 mm 4.9
11 Sept. Sunny
Sunny
 22° /14° 3.1 mm 4.8
12 Sept. Sunny
Sunny
 19° /14° 19.2 mm 4.6
13 Sept. Overcast
Overcast
 14° /9° 0 mm 3.2
14 Sept. Overcast
Overcast
 14° /10° 6.5 mm 4.3
15 Sept. Patchy rain possible
Patchy rain possible
 16° /11° 1.4 mm 4
16 Sept. Cloudy
Cloudy
 13° /8° 0 mm 4
17 Sept. Sunny
Sunny
 16° /10° 0 mm 5
18 Sept. Sunny
Sunny
 24° /14° 1 mm 6
19 Sept. Sunny
Sunny
 16° /9° 0 mm 4
20 Sept. Sunny
Sunny
 14° /10° 0.6 mm 4
21 Sept. Sunny
Sunny
 20° /13° 3.7 mm 5
22 Sept. Light rain shower
Light rain shower
 17° /12° 4.4 mm 4
23 Sept. Sunny
Sunny
 12° /5° 0 mm 4
24 Sept. Mist
Mist
 17° /10° 0 mm 4
25 Sept. Mist
Mist
 21° /11° 0 mm 5
26 Sept. Partly cloudy
Partly cloudy
 19° /10° 0 mm 5
27 Sept. Fog
Fog
 20° /10° 0 mm 5
28 Sept. Mist
Mist
 22° /10° 0 mm 5
29 Sept. Sunny
Sunny
 20° /11° 0.6 mm 5
30 Sept. Light rain shower
Light rain shower
 18° /10° 1.1 mm 4
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 19° 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?
Significant rainfall exceeding 113.7 mm is expected in Thunder Bay during September, occurring over more than 15 days. Preparing for wet conditions is recommended in your planning.

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 💧
Typically, Thunder Bay has 15 rainy days in September with a total of 113.7 mm of rainfall.

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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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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