S
M
T
W
T
F
S
30
86°
55°
31
77°
58°
1
78°
62°
2
77°
58°
3
81°
56°
4
82°
62°
5
85°
60°
6
85°
53°
7
76°
52°
8
75°
51°
9
75°
54°
10
81°
58°
11
80°
52°
12
73°
51°
13
74°
50°
14
76°
57°
15
79°
56°
16
81°
49°
17
74°
47°
18
71°
47°
19
71°
49°
20
72°
52°
21
69°
53°
22
69°
49°
23
70°
53°
24
70°
47°
25
72°
55°
26
75°
55°
27
76°
46°
28
73°
47°
29
68°
53°
30
72°
54°
1
67°
53°
2
69°
50°
3
66°
44°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Ontario
Ontario's September 2026 forecast shows daily high temperatures ranging from 66° to 86°, with overnight lows between 44° and 62°. The average high for September is 75° with an average low of 53°. 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 Ontario. See also: October | November | December.
