S
M
T
W
T
F
S
30
70°
57°
31
74°
54°
1
72°
52°
2
73°
49°
3
70°
47°
4
73°
49°
5
75°
55°
6
72°
56°
7
72°
53°
8
70°
53°
9
73°
54°
10
76°
52°
11
75°
55°
12
74°
52°
13
73°
55°
14
75°
53°
15
74°
45°
16
68°
44°
17
63°
49°
18
64°
53°
19
73°
52°
20
70°
51°
21
72°
42°
22
70°
39°
23
69°
42°
24
68°
46°
25
Hist. Avg.
63°
45°
26
Hist. Avg.
63°
44°
27
Hist. Avg.
62°
44°
28
Hist. Avg.
62°
44°
29
Hist. Avg.
61°
43°
30
Hist. Avg.
61°
43°
1
Hist. Avg.
61°
43°
2
Hist. Avg.
60°
42°
3
Hist. Avg.
60°
42°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Ottawa
Ottawa's September 2026 forecast shows daily high temperatures ranging from 63° to 76°, with overnight lows between 39° and 57°. The average high for September is 71° with an average low of 50°. 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.
