Annual mean 4°C · wettest around January · prevailing wind W
Warmest
22.4 °C
Coldest
-10.3 °C
Wettest
40%
Windiest
5.7 m/s
Prevailing
W
4.9 m/s average
When this place is good five ratings · thirty-six ten-day sections · click a cell to read it
never good
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Every reading
bars actual · line feels-like, °Cchance of rain, %wind speed, m/ssky covered, %
The average temperature in Thunder Bay over the whole year is 4°C. July is the hottest month, with highs of about 21°C; February is the coldest, with lows of about -13°C. Thunder Bay has no sharply defined rainy season: the chance of rain on a given day runs from 11% in March, the driest month, to 20% in January, the wettest. Winds in Thunder Bay are highest in November, averaging 4.8 m/s (17 km/h), and lightest in July, at 3.5 m/s (13 km/h). The prevailing wind is from the W. The clearest skies in Thunder Bay come in July, when the sky is typically 43% covered; December is the cloudiest month, at 61%.
Month by month Thunder Bay climate by month: average temperatures year round · click a month to read it
Month
High
Low
Feels like
Chance of rain
Cloud
Wind
Being outside
Sun
Walking
January
-9°C
-12°C
-15°C
20%
56%
4.6 m/s
0
0
0
February
-8°C
-13°C
-15°C
18%
51%
4.6 m/s
0
0
0
March
-1°C
-7°C
-7°C
11%
49%
4.5 m/s
0
0
2
April
4°C
-1°C
-1°C
18%
51%
4.6 m/s
0
0
13
May
12°C
6°C
8°C
15%
49%
4.1 m/s
15
0
52
June
17°C
12°C
15°C
15%
49%
3.8 m/s
50
6
76
July
21°C
15°C
21°C
12%
43%
3.5 m/s
79
22
64
August
21°C
15°C
20°C
12%
48%
3.6 m/s
79
16
70
September
17°C
11°C
15°C
17%
53%
3.7 m/s
51
5
76
October
10°C
5°C
5°C
13%
57%
4.4 m/s
10
1
39
November
1°C
-2°C
-4°C
16%
58%
4.8 m/s
1
0
9
December
-6°C
-8°C
-12°C
16%
61%
4.8 m/s
0
0
0
High and low are the warmest and coolest of four readings a day — midnight, 6am, noon and 6pm — so a true overnight low can sit a degree or two under them. Chance of rain, cloud and wind are the day’s average; feels-like and the three ratings (each out of 100: Good from 55, Ideal from 80) are read at midday.
Seasons, and the year in short Thunder Bay weather by season
Year round, Thunder Bay has days of about -9°C at their warmest in January, its coolest month, and 21°C in July, its warmest; the coolest hours of the day run from -13°C to 15°C through the year, and the average temperature over the year is 4°C around the clock. Rain is most likely around January and least likely around March. Every figure here is a decade of observations blended into one representative year, so it reads as what this date is usually like, not a forecast for one particular day.
Thunder Bay weather in winterDecember to February
High -8°CLow -11°CRain 18%
Winter in Thunder Bay has typical daily highs of about -8°C and lows of about -11°C, with a 18% chance of rain on a given day.
Thunder Bay weather in springMarch to May
High 5°CLow -1°CRain 15%
Spring in Thunder Bay has typical daily highs of about 5°C and lows of about -1°C, with a 15% chance of rain on a given day.
Thunder Bay weather in summerJune to August
High 20°CLow 14°CRain 13%
Summer in Thunder Bay has typical daily highs of about 20°C and lows of about 14°C, with a 13% chance of rain on a given day.
Thunder Bay weather in autumnSeptember to November
High 9°CLow 5°CRain 15%
Autumn in Thunder Bay has typical daily highs of about 9°C and lows of about 5°C, with a 15% chance of rain on a given day.
When is the rainy season in Thunder Bay?
Thunder Bay has no sharply defined rainy season: the chance of rain on a given day runs from 11% in March, the driest month, to 20% in January, the wettest.
What time of year is Thunder Bay windiest?
Winds in Thunder Bay are highest in November, averaging 4.8 m/s (17 km/h), and lightest in July, at 3.5 m/s (13 km/h). The prevailing wind is from the W.
What is the average temperature in Thunder Bay year round?
The average temperature in Thunder Bay over the whole year is 4°C. July is the hottest month, with highs of about 21°C; February is the coldest, with lows of about -13°C.