Our verdict
The best time to visit Thunder Bay is September-November
In summer, the temperature in Thunder Bay can rise as high as 23℃ (74℉). The coldest it usually gets in winter-time in Thunder Bay is around -21℃ (-6℉).
If you’re keen to work on your tan in Thunder Bay, you’re most likely get the longest days between sun-up and sun-down around July. On average it rains the most days in May, making it the wettest month of the year. Although it’s the wet season, it can often rain a little bit during the day or evening but have fine weather for a majority of the day too, so don’t let this put you off.
Continue reading to find out more about when to visit Thunder Bay, including the climate, seasonal info, what to pack, FAQs, and the best tools to help you plan and book your next vacation.
Quick links: Fast facts / Seasons / Average temperatures / Monthly climate / FAQs / Map
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Thunder Bay seasons
Before you continue, it’s important to know when the seasons are in Thunder Bay as they might be different to yours depending on where in the world you’re travelling from. Thunder Bay is in the Northern Hemisphere, so the seasons fall during these months:
| Season | Months |
|---|---|
| Summer | June to August |
| Autumn/fall | September to November |
| Winter | December to February |
| Spring | March to May |
Average temperatures in Thunder Bay
If the temperature is a big factor for you to help you decide when to visit, the chart below shows the average minimum and maximum temperatures in Thunder Bay for each month side-by-side so you can easily see the difference in weather throughout the year. To see the temperatures in both Celsius (°C) and Fahrenheit (°F), hover or tap the shaded boxes on the graph.
Thunder Bay climate by month
If you already have a rough idea about which months you might want to travel, the section below shows a detailed breakdown of the climate in Thunder Bay for each month so you can see if it all suits your wants and needs. Scroll down, or use the quick menu below to jump to your preferred month.
Jump to:
Thunder Bay in January
- Average temperature: -12℃ (10℉)
- Average high temperature: -9℃ (16℉)
- Average low temperature: -16℃ (4℉)
- Average humidity: 90%
- Average sunny days: 11 days
- Average rainfall: 27mm (1") over 5 days
- Average snow days: 22 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in January, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Thunder Bay in February
- Average temperature: -11℃ (12℉)
- Average high temperature: -8℃ (18℉)
- Average low temperature: -15℃ (5℉)
- Average humidity: 90%
- Average sunny days: 11 days
- Average rainfall: 27mm (1") over 4 days
- Average snow days: 20 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in February, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Thunder Bay in March
- Average temperature: -4℃ (24℉)
- Average high temperature: -1℃ (30℉)
- Average low temperature: -8℃ (18℉)
- Average humidity: 87%
- Average sunny days: 10 days
- Average rainfall: 34mm (1") over 11 days
- Average snow days: 17 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in March, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Thunder Bay in April
- Average temperature: 1℃ (35℉)
- Average high temperature: 5℃ (40℉)
- Average low temperature: -2℃ (29℉)
- Average humidity: 79%
- Average sunny days: 13 days
- Average rainfall: 44mm (2") over 10 days
- Average snow days: 10 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in April, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Thunder Bay in May
- Average temperature: 8℃ (47℉)
- Average high temperature: 12℃ (54℉)
- Average low temperature: 4℃ (39℉)
- Average humidity: 70%
- Average sunny days: 17 days
- Average rainfall: 45mm (2") over 13 days
- Average snow days: 1 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in May, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Thunder Bay in June
- Average temperature: 12℃ (54℉)
- Average high temperature: 17℃ (62℉)
- Average low temperature: 8℃ (46℉)
- Average humidity: 74%
- Average sunny days: 17 days
- Average rainfall: 38mm (2") over 12 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in June, make sure you pack a warm jacket or coat.
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Thunder Bay in July
- Average temperature: 16℃ (61℉)
- Average high temperature: 21℃ (70℉)
- Average low temperature: 12℃ (53℉)
- Average humidity: 74%
- Average sunny days: 18 days
- Average rainfall: 34mm (1") over 12 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in July, make sure you pack a coat or jumper for the evenings and some light clothes for the daytime.
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Thunder Bay in August
- Average temperature: 17℃ (62℉)
- Average high temperature: 21℃ (70℉)
- Average low temperature: 13℃ (55℉)
- Average humidity: 76%
- Average sunny days: 18 days
- Average rainfall: 30mm (1") over 11 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in August, make sure you pack a light jumper or hoodie for the evenings and some light clothes for the daytime.
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Thunder Bay in September
- Average temperature: 12℃ (54℉)
- Average high temperature: 17℃ (62℉)
- Average low temperature: 9℃ (48℉)
- Average humidity: 79%
- Average sunny days: 18 days
- Average rainfall: 44mm (2") over 11 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in September, make sure you pack a warm jacket or coat.
Thunder Bay in October
- Average temperature: 6℃ (43℉)
- Average high temperature: 9℃ (48℉)
- Average low temperature: 3℃ (38℉)
- Average humidity: 80%
- Average sunny days: 17 days
- Average rainfall: 45mm (2") over 11 days
- Average snow days: 2 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in October, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Thunder Bay in November
- Average temperature: -1℃ (30℉)
- Average high temperature: 1℃ (34℉)
- Average low temperature: -4℃ (26℉)
- Average humidity: 82%
- Average sunny days: 13 days
- Average rainfall: 38mm (2") over 8 days
- Average snow days: 13 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in November, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Thunder Bay in December
- Average temperature: -8℃ (17℉)
- Average high temperature: -6℃ (22℉)
- Average low temperature: -11℃ (12℉)
- Average humidity: 88%
- Average sunny days: 10 days
- Average rainfall: 35mm (1") over 5 days
- Average snow days: 20 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Thunder Bay in December, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
Add visitor or local insider tips >