S
M
T
W
T
F
S
30
75°
59°
31
71°
60°
1
75°
62°
2
77°
60°
3
75°
59°
4
77°
61°
5
70°
55°
6
69°
52°
7
76°
56°
8
75°
57°
9
74°
56°
10
71°
55°
11
72°
55°
12
74°
55°
13
74°
54°
14
72°
56°
15
74°
55°
16
74°
53°
17
67°
53°
18
72°
52°
19
69°
53°
20
68°
54°
21
71°
54°
22
71°
53°
23
72°
52°
24
68°
48°
25
59°
46°
26
63°
47°
27
67°
47°
28
68°
50°
29
69°
50°
30
69°
49°
1
68°
49°
2
68°
50°
3
66°
49°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Ottawa
Ottawa's September 2026 forecast shows daily high temperatures ranging from 59° to 77°, with overnight lows between 46° and 62°. The average high for September is 71° with an average low of 54°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how September weather will actually feel in Ottawa. See also: October | November | December.
