Thunder Bay climate — normals and trends
Thunder Bay (Canada) has a warm-summer humid continental climate (Dfb) under the Köppen-Geiger classification. Its mean annual temperature is 2.6 °C and it receives 669 mm of precipitation per year.
These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.
The warmest month is July (18.0 °C on average) and the coldest is January (-14.6 °C). Rainfall peaks in September.
Thunder Bay averages 176 frost days, 0 hot days (≥ 30 °C) and 107 rainy days per year.
Thunder Bay has warmed by +1.5 °C between 1940 and 2025, or +0.17 °C per decade. This trend is statistically significant.
The hottest day of the period reached 33.0 °C (on 7 August 2001) and the coldest -38.6 °C (on 15 January 1972).
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
Climate normals · ERA5
Thunder BayOntario
- coords
- 48.38°, -89.25°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
2.6°C
Average daily high
6.6°C
Average daily low
-1.3°C
Annual rainfall
669mm
Sunshine / day
8.7h
Mean relative humidity
76%
Average peak wind
18.0km/h
Seasonal range
32.6°C
Frost days (< 0 °C)
176 d/yr
Hot days (≥ 30 °C)
0 d/yr
Rainy days (≥ 1 mm)
107 d/yr
Annual snowfall
131.7 cm
Average feels-like high
3.7 °C
Average feels-like low
-5.1 °C
Average peak gust
37.9 km/h
Tropical nights (≥ 20 °C)
1 d/yr
Solar radiation
13.5 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.5 °C
since 1940
+0.2 °C per decade · r² = 0.19 · p = < 0.001
Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).
A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.
Records for the period
Hottest day
33.0 °C
7 August 2001
Coldest day
-38.6 °C
15 January 1972
Wettest day
86 mm
14 August 1988
Windiest day
48.5 km/h
24 December 2022
Strongest gust
109.1 km/h
17 October 1984
Hottest feels-like
38.9 °C
30 July 1975
Coldest feels-like
-45.1 °C
15 January 1972
Snowiest day
27.4 cm
8 November 1943
Sunniest day
15.9 h
21 June 1963
Normals computed over complete calendar years 1940–2025.
A specific year
Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?
Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | -9.6 °C | +0.9 °C | 33 mm | +3 mm |
| Feb | -8.1 °C | +0.1 °C | 41 mm | +18 mm |
| Mar | 0.8 °C | +2.6 °C | 46 mm | +8 mm |
| Apr | 5.1 °C | -0.4 °C | 93 mm | +39 mm |
| May | 14.4 °C | +2.0 °C | 27 mm | -39 mm |
| Jun | 19.0 °C | +0.9 °C | 130 mm | +55 mm |
| Jul | 22.2 °C | 0.0 °C | 80 mm | +9 mm |
| Aug | 21.5 °C | +0.1 °C | 40 mm | -35 mm |
| Sep | 17.8 °C | +1.5 °C | 43 mm | -38 mm |
| Oct | 12.7 °C | +3.1 °C | 62 mm | -3 mm |
| Nov | 2.2 °C | +1.1 °C | 37 mm | -19 mm |
| Dec | -7.2 °C | -0.7 °C | 61 mm | +24 mm |
The year's extremes
What was the weather like that day?
Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.
Frequently asked questions
What is the climate of Thunder Bay?
Thunder Bay has a warm-summer humid continental climate (Köppen Dfb). Over 1940-2025, the average annual temperature is 2.6 °C and it receives 669 mm of precipitation per year.
What is the hottest day ever recorded in Thunder Bay?
The hottest day measured in Thunder Bay between 1940 and 2025 was 7 August 2001, reaching 33.0 °C.
What is the coldest day in Thunder Bay?
The coldest day measured in Thunder Bay between 1940 and 2025 was 15 January 1972, at -38.6 °C.
Does it snow in Thunder Bay?
Yes. Thunder Bay gets on average 131.7 cm of snow per year and has around 176 frost days.
Has the climate of Thunder Bay warmed?
Yes: Thunder Bay warmed by +1.5 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Thunder Bay?
The wettest day measured in Thunder Bay between 1940 and 2025 was 14 August 1988, with 86 mm of rain in 24 hours.
What was the windiest day in Thunder Bay?
The windiest day measured in Thunder Bay between 1940 and 2025 was 24 December 2022, with winds reaching 48.5 km/h.
What is the warmest month in Thunder Bay?
The warmest month in Thunder Bay is July (18.0 °C on average); the coldest is January (-14.6 °C).
How much does it rain in Thunder Bay?
Thunder Bay receives on average 669 mm of precipitation per year, spread over about 107 rainy days.
Is it sunny in Thunder Bay?
Thunder Bay gets on average 8.7 hours of sunshine per day, roughly 3,175 hours per year over 1940-2025.
What is the biggest single-day snowfall in Thunder Bay?
The heaviest 24-hour snowfall measured in Thunder Bay between 1940 and 2025 was 8 November 1943, with 27.4 cm.
Are there tropical nights in Thunder Bay?
Yes: Thunder Bay has on average 1 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Thunder Bay?
In Thunder Bay, between 1940 and 2025, the highest apparent temperature reached 38.9 °C on 30 July 1975, and the lowest was -45.1 °C on 15 January 1972.
Compare Thunder Bay with another city
Pick a second city: its normals will be set against these, indicator by indicator.