S
M
T
W
T
F
S
30
85°
64°
31
87°
65°
1
82°
60°
2
81°
59°
3
81°
59°
4
80°
57°
5
80°
58°
6
83°
63°
7
84°
63°
8
83°
58°
9
82°
57°
10
80°
56°
11
82°
62°
12
84°
62°
13
84°
61°
14
83°
61°
15
84°
60°
16
83°
61°
17
84°
62°
18
82°
60°
19
81°
59°
20
82°
59°
21
81°
57°
22
81°
52°
23
74°
55°
24
Hist. Avg.
78°
54°
25
Hist. Avg.
77°
54°
26
Hist. Avg.
77°
54°
27
Hist. Avg.
76°
53°
28
Hist. Avg.
76°
53°
29
Hist. Avg.
75°
52°
30
Hist. Avg.
75°
52°
1
Hist. Avg.
75°
51°
2
Hist. Avg.
74°
51°
3
Hist. Avg.
74°
50°
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 74° to 87°, with overnight lows between 52° and 65°. The average high for September is 82° with an average low of 60°. 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.
