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Thunder Bay (ON) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit Thunder Bay.
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Climate overview of Thunder Bay
Thunder Bay, Ontario, Canada, experiences significant temperature variation throughout the year. Summers bring daytime highs of 23°C (73°F) in August, while winters cool to -8°C (18°F) in January.
The city receives around 744 mm (29 in) of rain/snowfall per year. It experiences a distinct dry season from January to March, with warm summers and very cold winters. September is the wettest month and February the driest.
Thunder Bay Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Thunder Bay - and find the best time to visit.
Monthly Temperature in Thunder Bay
Depending on the time of the year, temperatures range from comfortable to very cold in Thunder Bay. On average, daytime temperatures range from a comfortable 23°C (73°F) in August to a very cold -8°C (18°F) in January.
Nighttime temperatures range from 14°C (57°F) in August to -17°C (1°F) in January.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in Thunder Bay
Generally, Thunder Bay has a moderate amount of precipitation, averaging 744 mm (29 in) of rain/snowfall annually. The seasons in Thunder Bay bring significant changes in precipitation. The wettest month, September, receives moderate rainfall, with an average of 93 mm (3.7 in) of precipitation. This rainfall is distributed across 13 rainy days.
In contrast, the driest month, February, experiences much less snowfall, totaling 30 mm (1.2 in) over 9 snowy days. These distinct seasonal differences provide diverse experiences throughout the year. For more details, please visit our Thunder Bay Precipitation page.
The mean monthly precipitation over the year, including rain, hail, and snow
The average number of days each month with precipitation
Best Time to Visit Thunder Bay
The most comfortable overall weather for exploring Thunder Bay is usually found in July and August. Conditions are generally least comfortable in January, February, March, April, November and December.
Monthly ratings reflect general weather comfort, based on daytime temperature and rainfall. Swimming and winter conditions are highlighted separately where relevant.
Jan
very cold
Feb
very cold
Mar
cold
Apr
cold
May
mixed
Jun
very good
Jul
excellent
Aug
excellent
Sep
very good
Oct
mixed
Nov
cold
Dec
very cold
- Best overall: July and August
- Warmest weather: July and August
- Fewer rainy days: January, February, March, April and November
- Seasonal pattern: A distinct dry season from January to March, with warm summers and very cold winters
- Coldest conditions: January, with freezing nights around -17°C (1°F).
Frequently asked questions about the climate in Thunder Bay
What is the best time to visit Thunder Bay?
July and August typically offer the most optimal weather in Thunder Bay. In contrast, January, February, March, April, November and December tend to have less optimal conditions. Thunder Bay has a distinct dry season from January to March, with warm summers and very cold winters.
What temperatures can I expect in Thunder Bay?
Daytime highs range from -8°C (18°F) in January to 23°C (73°F) in August. Nighttime lows range from -17°C (1°F) to 14°C (57°F). Temperatures vary considerably through the year.
How much rain does Thunder Bay get?
Annual rainfall is around 744 mm (29 in). September is the wettest month with 93 mm (3.7 in), while February is the driest with 30 mm (1.2 in).
Thunder Bay 3-Day Forecast
Thunder Bay on the map
Thunder Bay is highlighted - select any city to see its climate.
Popular in September
Where to go in September - average daytime high across popular destinations.
Toronto
22°C (72°F) Niagara Falls23°C (73°F) Montréal
22°C (72°F) Ottawa22°C (72°F) Quebec City
20°C (68°F) Vancouver19°C (66°F) Calgary19°C (66°F) Whistler15°C (59°F) Bucket list
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