S
M
T
W
T
F
S
30
83°
52°
31
73°
52°
1
73°
60°
2
78°
59°
3
72°
52°
4
75°
59°
5
80°
51°
6
74°
52°
7
72°
51°
8
70°
49°
9
70°
49°
10
71°
54°
11
74°
48°
12
70°
47°
13
69°
48°
14
73°
52°
15
74°
48°
16
70°
46°
17
67°
45°
18
65°
44°
19
65°
46°
20
66°
49°
21
65°
50°
22
65°
45°
23
67°
52°
24
70°
49°
25
71°
54°
26
72°
52°
27
72°
45°
28
67°
42°
29
62°
48°
30
65°
52°
1
63°
53°
2
67°
49°
3
68°
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 62° to 83°, with overnight lows between 42° and 60°. The average high for September is 70° with an average low of 50°. 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.
