S
M
T
W
T
F
S
30
78°
67°
31
89°
67°
1
92°
72°
2
92°
72°
3
93°
72°
4
95°
68°
5
89°
68°
6
83°
62°
7
82°
63°
8
86°
68°
9
86°
67°
10
80°
61°
11
81°
58°
12
82°
60°
13
80°
59°
14
79°
60°
15
80°
58°
16
77°
54°
17
80°
59°
18
72°
58°
19
74°
59°
20
78°
58°
21
76°
59°
22
76°
57°
23
73°
56°
24
74°
55°
25
78°
56°
26
77°
51°
27
67°
46°
28
65°
44°
29
65°
47°
30
66°
44°
1
65°
46°
2
69°
53°
3
65°
51°
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 65° to 95°, with overnight lows between 44° and 72°. The average high for September is 77° with an average low of 57°. 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.
