Weather in Thunder Bay: September
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Average day temperature: | 62.8°F |
| Average night temperature: | 53.2°F | |
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Sea water temperature: | 60.2°F |
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Number of sunny days: | 14 days |
| Day length: | 11.7 - 13.4 hours | |
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Number of rainy days: | 2 days |
| Precipitation totals: | 0.7 in. | |
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forecast
| Thunder Bay |
temperature
| Thunder Bay |
Air temperature in September, °F
The highest day temperature during September of 2025 was 77°F. At the same time the lowest night temperature was 40°F. Daily and nightly averages during September were 63.3°F and 52.1°F.
Sea water temperature in Thunder Bay in September, °F
The average sea water temperature in September of 2025 was 59.9°F. The highest and lowest sea temperatures during the month were 62.2°F and 57.4°F.
Mostly all days in September are sunny but cloudy days are also possible.
Precipitation total in September, in.
Precipitation total value in Thunder Bay in September is 0.7 in. Other months of the year show relatively similar values.
The average wind speed value in September is 6.9 mph
This chart shows average number of hours during the day when sunlight can reach the ground. It depends on day length and cloudiness during the day. The average number of sunny hours in September is: 7.4.
Best time for vacation in Thunder Bay
Thunder Bay on a weather map
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