Measurements:
°C
°F
Thunder Bay
40°F
SE 8 mph
Feels like: 34°F
Precip: 0%
World Resorts Canada Thunder Bay Weather

Thunder Bay Sea Water Temperature

Current Sea Water Temperature:
+37.8°F
Maximum Sea Water Temperature in May: 53.6°F
Minimum Sea Water Temperature in May: 32.2°F
Average water temperature in May: 38.8°F

Sea Water Temperature for the Last 10 Days:

May 19 37.8°F May 14 39.0°F
May 18 37.8°F May 13 34.8°F
May 17 39.8°F May 12 35.0°F
May 16 37.6°F May 11 35.0°F
May 15 35.0°F May 10 33.8°F

When is the Warmest Sea for Thunder Bay?

According to our data for the last three years for Thunder Bay the highest average sea water temperature was in August, September and July.

Average Water Temperature by Month, °F

Sea Water Temperature in August

Select Year: 2025 2024 2023

The average sea surface temperature in August 2025 for Thunder Bay was 64.6°F. The maximum and minimum values were 61.0°F and 70.0°F respectively.

Sea Water Temperature in September

Select Year: 2025 2024 2023

The average sea surface temperature in September 2025 for Thunder Bay was 61.0°F. The maximum and minimum values were 58.2°F and 63.6°F respectively.

Sea Water Temperature in July

Select Year: 2025 2024 2023

The average sea surface temperature in July 2025 for Thunder Bay was 62.4°F. The maximum and minimum values were 55.8°F and 66.6°F respectively.

Best Time to Visit Thunder Bay
The most sunny months:
September 14 days
August 14 days
July 12 days
The most warm months:
July 71.5 °F
August 71.2 °F
June 64.4 °F
Warmest sea temperature:
August 64.9 °F
September 61.3 °F
July 60.6 °F
The most cold months:
January 9.8 °F
February 11.1 °F
December 17.9 °F
The most rainy months:
September 2 days
August 2 days
April 2 days
The most windy months:
November 9 mph
December 9 mph
April 8 mph

Thunder Bay on the Weather Map

24 Hours Weather Forecast
Thunder Bay
Local time: 07:52
19 may, tuesday
0900 40°F
SE
8 mph
1200 38°F
SE
11 mph
1500 40°F
SE
12 mph
1800 42°F
SE
12 mph
2100 38°F
SE
11 mph
20 may, wednesday
0000 32°F
SE
7 mph
0300 30°F
SE
8 mph
0600 30°F
SE
9 mph