S
M
T
W
T
F
S
30
82°
58°
31
83°
63°
1
83°
63°
2
81°
57°
3
81°
53°
4
75°
53°
5
74°
57°
6
75°
61°
7
81°
59°
8
79°
55°
9
75°
54°
10
74°
60°
11
75°
59°
12
81°
60°
13
81°
60°
14
80°
59°
15
80°
56°
16
78°
58°
17
72°
50°
18
75°
50°
19
70°
48°
20
69°
46°
21
67°
47°
22
69°
55°
23
69°
48°
24
71°
47°
25
69°
54°
26
72°
53°
27
70°
54°
28
75°
52°
29
76°
48°
30
73°
47°
1
68°
52°
2
73°
51°
3
66°
44°
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 66° to 83°, with overnight lows between 44° and 63°. The average high for September is 75° 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.
