Thunder Bay
September
Weather in Thunder Bay for September 2025
Your guide to Thunder Bay weather in September - trends and predictions
In general, the average temperature in Thunder Bay at the beginning of September is 22.7 °C. As the month progressed, temperatures tended to significantly cool down, reaching an average of 19.3 °C by the end of September.
Thunder Bay experiences moderate rainfall in September, with an average of 9 rainy days and a total precipitation of 58.2 mm.
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Temperatures
Rain 🌧️
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21
Dry days
9
Rainy days
0
Snow days
20°/11°
Temperatures
15 km/h
Avg max wind
77 %
Avg humidity
Thunder Bay Weather September
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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
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| 1 Sept. |  Patchy rain possible | 22° /10° | 0.1 mm | 6 | |
| 2 Sept. |  Sunny | 26° /12° | 0 mm | 7 | |
| 3 Sept. |  Partly cloudy | 27° /14° | 0.2 mm | 7 | |
| 4 Sept. | Partly cloudy | 24° /15° | 0 mm | 6 | |
| 5 Sept. |  Fog | 24° /12° | 6.2 mm | 6 | |
| 6 Sept. | Light rain shower | 17° /7° | 16.5 mm | 4 | |
| 7 Sept. | Partly cloudy | 19° /5° | 0 mm | 6 | |
| 8 Sept. | Mist | 20° /5° | 0 mm | 5 | |
| 9 Sept. |  Light drizzle | 18° /10° | 5.9 mm | 5 | |
| 10 Sept. | Light rain shower | 20° /11° | 1.5 mm | 5 | |
| 11 Sept. |  Overcast | 19° /11° | 0 mm | 5 | |
| 12 Sept. | Overcast | 18° /9° | 0 mm | 5 | |
| 13 Sept. | Sunny | 21° /9° | 0 mm | 6 | |
| 14 Sept. | Mist | 19° /8° | 0 mm | 5 | |
| 15 Sept. | Mist | 22° /13° | 0.9 mm | 5 | |
| 16 Sept. | Mist | 21° /13° | 3.7 mm | 5 | |
| 17 Sept. | Overcast | 19° /11° | 6.2 mm | 5 | |
| 18 Sept. | Overcast | 19° /11° | 7.8 mm | 5 | |
| 19 Sept. | Mist | 19° /10° | 0 mm | 5 | |
| 20 Sept. | Patchy rain possible | 20° /14° | 0.5 mm | 5 | |
| 21 Sept. | Mist | 21° /12° | 0 mm | 5 | |
| 22 Sept. | Light rain shower | 18° /11° | 6 mm | 4 | |
| 23 Sept. | Patchy rain possible | 17° /9° | 0 mm | 5 | |
| 24 Sept. | Overcast | 17° /9° | 0 mm | 4 | |
| 25 Sept. | Overcast | 21° /10° | 0 mm | 5 | |
| 26 Sept. | Partly cloudy | 19° /11° | 0 mm | 5 | |
| 27 Sept. | Fog | 19° /10° | 0 mm | 5 | |
| 28 Sept. | Mist | 20° /10° | 0 mm | 5 | |
| 29 Sept. | Fog | 19° /11° | 0.9 mm | 5 | |
| 30 Sept. | Light rain shower | 20° /9° | 1.7 mm | 5 | |
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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.
Change Month
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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