S
M
T
W
T
F
S
30
92°
64°
31
93°
68°
1
93°
68°
2
92°
67°
3
93°
68°
4
93°
69°
5
92°
68°
6
91°
66°
7
91°
62°
8
84°
66°
9
83°
65°
10
84°
66°
11
89°
65°
12
89°
66°
13
88°
65°
14
89°
61°
15
87°
60°
16
79°
55°
17
78°
55°
18
79°
59°
19
83°
54°
20
78°
53°
21
76°
56°
22
77°
56°
23
78°
60°
24
83°
61°
25
83°
61°
26
84°
60°
27
83°
59°
28
81°
56°
29
80°
55°
30
81°
55°
1
79°
54°
2
82°
58°
3
73°
48°
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 73° to 93°, with overnight lows between 48° and 69°. The average high for September is 85° with an average low of 61°. 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.
