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Thunder Bay September Weather

Averages and records for weather in Thunder Bay, Ontario in the month of September.

Typical Thunder Bay September Weather 1991–2020
Average daily high	18.8 °C
Average daily low	5.5 °C
Average monthly precipitation	6.5 cm
Daily chance of precipitation	46.9%

Thunder Bay September Weather Records 1941–2024
Highest temperature	34.1 °C	September 11, 2005
Lowest temperature	-8.3 °C	September 29, 1945
Highest daily low	18.3 °C	September 11, 2003
Lowest daily high	3.7 °C	September 25, 1984
Hottest average high temperature	22.1 °C	2009
Coldest average high temperature	13.9 °C	1965
Most daily precipitation	13.1 cm	September 8, 1977
Most monthly precipitation	28.4 cm	1977

Note: Daily averages are a moving average which includes 14 days before and after

Day	Average (°C)		Record (°C)
Day	High	Low	High	Low
September 1	21.8	8.2	31.1	-1.1
September 2	21.7	8.1	32.6	-2.2
September 3	21.6	8.0	32.8	-2.2
September 4	21.4	7.9	29.4	-1.1
September 5	21.2	7.7	33.1	-1.1
September 6	21.0	7.5	30.6	-0.4
September 7	20.8	7.4	30.0	-1.7
September 8	20.6	7.2	31.3	-1.7
September 9	20.3	6.9	30.7	-3.3
September 10	20.1	6.6	28.3	-2.2
September 11	19.9	6.5	34.1	-1.1
September 12	19.7	6.3	30.0	-2.2
September 13	19.5	6.1	27.2	-2.2
September 14	19.2	5.9	28.2	-1.1
September 15	19.0	5.7	25.9	-4.4
September 16	18.7	5.5	26.7	-4.2
September 17	18.4	5.2	27.2	-3.6
September 18	18.2	4.9	30.6	-4.4
September 19	17.9	4.7	28.4	-4.4
September 20	17.6	4.5	27.2	-5.0
September 21	17.3	4.2	28.9	-5.0
September 22	17.1	4.1	26.1	-4.4
September 23	16.8	3.9	28.0	-6.8
September 24	16.6	3.7	29.0	-4.0
September 25	16.4	3.6	24.1	-8.3
September 26	16.2	3.4	25.0	-4.4
September 27	16.0	3.2	26.6	-5.6
September 28	15.8	3.0	25.7	-8.3
September 29	15.5	2.8	24.7	-8.3
September 30	15.2	2.7	26.1	-6.1

Weather Station Details

Years	Station	Coordinates
2004–2024	Thunder Bay CS	location
1941–2003	Thunder Bay A	location