Thunder Bay Average Temperature by Month

This page shows the average temperature in each month of the year in Thunder Bay, Ontario. It is based on NOAA data for the years 1991–2020.
What's the Hottest Month in Thunder Bay?
In Thunder Bay, Ontario, the warmest month is July, with an average daily high temperature of 24.6 °C and an average low of 11.0 °C.
What's the Coldest Month in Thunder Bay?
In Thunder Bay, Ontario, the coolest month is January, with an average daily high temperature of -7.8 °C and an average low of -19.0 °C.
Month Avg. High Avg. Low
January -7.8 °C -19.0 °C
February -5.3 °C -18.6 °C
March 1.0 °C -11.4 °C
April 8.7 °C -4.1 °C
May 16.0 °C 2.0 °C
June 21.5 °C 7.7 °C
July 24.6 °C 11.0 °C
August 24.0 °C 10.0 °C
September 18.8 °C 5.5 °C
October 10.6 °C -0.4 °C
November 2.4 °C -6.6 °C
December -4.4 °C -14.5 °C
Year 9.4 °C -3.1 °C
Weather Station Details
Years Station Coordinates
2004–2024 Thunder Bay CS location
1941–2003 Thunder Bay A location
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