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Ottawa September Weather

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

Typical Ottawa September Weather 1991–2020
Average daily high	21.3 °C
Average daily low	10.5 °C
Average monthly precipitation	8.7 cm
Average monthly snow	none
Daily chance of precipitation	39.9%
Daily chance of snow	0%

Ottawa September Weather Records 1889–2024
Highest temperature	36.7 °C	September 11, 1931
Lowest temperature	-4.4 °C	September 28, 1947
Highest daily low	22.4 °C	September 9, 2001
Lowest daily high	5.6 °C	September 29, 1963
Hottest average high temperature	25.7 °C	2023
Coldest average high temperature	16.5 °C	1928
Most daily precipitation	10.9 cm	September 9, 2004
Most monthly precipitation	16.8 cm	1986
Most daily snow	none	-
Most monthly snow	none	-

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	23.8	12.9	35.6	3.9
September 2	23.6	12.7	34.4	2.2
September 3	23.5	12.6	34.4	2.8
September 4	23.4	12.5	35.0	2.2
September 5	23.2	12.3	33.5	2.8
September 6	23.1	12.1	32.5	0.6
September 7	23.0	12.0	33.0	2.2
September 8	22.9	11.9	34.8	1.1
September 9	22.6	11.7	35.3	1.7
September 10	22.4	11.5	34.4	0.0
September 11	22.2	11.3	36.7	1.1
September 12	22.1	11.1	33.3	1.7
September 13	21.9	10.9	34.4	-0.6
September 14	21.7	10.8	30.6	-1.7
September 15	21.5	10.6	32.2	-1.1
September 16	21.2	10.4	32.8	-1.1
September 17	20.9	10.3	30.0	0.0
September 18	20.7	10.1	30.6	-0.6
September 19	20.4	9.9	31.1	-0.7
September 20	20.2	9.7	32.0	-2.2
September 21	19.9	9.5	32.2	-2.2
September 22	19.6	9.3	33.3	-2.2
September 23	19.4	9.0	30.0	-1.1
September 24	19.2	8.8	31.0	-1.7
September 25	19.0	8.6	33.0	-0.6
September 26	18.8	8.5	30.5	-2.8
September 27	18.5	8.3	30.5	-1.7
September 28	18.3	8.0	27.8	-4.4
September 29	18.1	7.8	28.3	-2.7
September 30	17.9	7.6	28.3	-3.3

Weather Station Details

Years	Station	Coordinates
1889–2024	Ottawa CDA	location