Thunder Bay Temperatures: Averages by Month





The numbers here tell you how hot and cold the weather usually is in Thunder Bay, Ontario during each month of the year.

The average high and low temperatures are listed below monthly and annually for the city, in both degrees Fahrenheit and Celsius.

Maximums and minimums are only part of the temperature picture. To fill in the rest, there's information on how many days a month get above or below a given temperature.

To find out how often it rises over 10, 20 or 30 °C each month in Thunder Bay, scroll down farther. There are also monthly and yearly counts of days with frost and cold weather.

All the numbers are long-term historical averages based on climate data gathered from 1981 to 2010.

Average Thunder Bay temperatures
High °F Low °F   High °C Low °C
18 -5 January -8 -21
23 0 February -5 -18
33 13 March 1 -11
49 26 April 9 -3
61 36 May 16 2
69 45 June 21 7
76 52 July 24 11
74 51 August 23 10
64 42 September 18 6
50 30 October 10 -1
34 18 November 1 -8
22 3 December -6 -16
48 26 Year 9 -3

Days of Hot Weather in Thunder Bay

The hottest days at Thunder Bay usually have temperatures peaking in the low-thirties Celsius. The city averages six days a year with thirty-degree weather, which can show up from May to September. The temperature does climb over 35 °C (95 °F), but that's uncommon, happening on average just once every three years.

Days per month in Thunder Bay over 10, 20 or 30 °C
  10 °C
50 °F
20 °C
68 °F
30 °C
86 °F
January 0 0 0
February 0 0 0
March 1 0 0
April 12 1 0
May 27 8 1
June 30 16 1
July 31 26 3
August 31 24 2
September 28 10 0
October 14 1 0
November 2 0 0
December 0 0 0
Year 177 85 6

When Thunder Bay Has Frosty Weather

Thunder Bay typically has 203 days a year when the minimum temperature is at 0 °C or below. The average date for the last frost in spring is May 30. Frost normally returns here on September 19. The frost-free period extends for 111 days on average between the final spring frost and the first fall frost.

Average number of days with freezing temperatures in Thunder Bay
  0 °C
32 °F
January 31
February 28
March 29
April 23
May 11
June 0
July 0
August 0
September 4
October 19
November 28
December 30
Year 203

How Often Thunder Bay Has Cold Temperatures

Thunder Bay's chilliest winter nights have lows below -30 °C (-22 °F). The city averages eight nights a year, mainly in January and February, when the temperature gets that cold.

From October to April, Thunder Bay can remain below freezing all day long. The city typically has 96 days a year during which the temperature never rises above 0 °C.

Days per month on average in Thunder Bay when the minimum temperature drops below -2, -10, or -20 °C
  -2 °C
28 °F
-10 °C
14 °F
-20 °C
-4 °F
January 30 27 17
February 27 21 12
March 28 14 4
April 18 2 0
May 5 0 0
June 0 0 0
July 0 0 0
August 0 0 0
September 2 0 0
October 13 0 0
November 24 10 1
December 29 23 11
Year 175 98 45
Reference

Environment Canada. Meteorological Service of Canada. Canadian Climate Normals. 1981-2010 Climate Normals & Averages.

Ontario Temperatures
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