S
M
T
W
T
F
S
30
77°
64°
31
87°
71°
1
85°
73°
2
91°
73°
3
92°
69°
4
84°
67°
5
80°
62°
6
78°
55°
7
79°
55°
8
85°
58°
9
85°
68°
10
75°
57°
11
76°
58°
12
81°
64°
13
82°
64°
14
83°
69°
15
79°
60°
16
72°
55°
17
72°
55°
18
67°
50°
19
66°
48°
20
69°
49°
21
67°
52°
22
68°
57°
23
70°
56°
24
75°
57°
25
77°
57°
26
77°
56°
27
75°
56°
28
76°
58°
29
77°
58°
30
77°
57°
1
76°
56°
2
73°
49°
3
62°
46°
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 85°, with overnight lows between 46° and 69°. The average high for September is 74° with an average low of 56°. 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.
