S
M
T
W
T
F
S
30
74°
63°
31
71°
64°
1
82°
67°
2
78°
66°
3
76°
60°
4
75°
53°
5
73°
54°
6
73°
51°
7
76°
53°
8
75°
62°
9
78°
59°
10
71°
49°
11
66°
50°
12
69°
53°
13
71°
55°
14
71°
51°
15
72°
51°
16
71°
52°
17
74°
45°
18
65°
46°
19
70°
48°
20
73°
54°
21
73°
54°
22
72°
52°
23
70°
52°
24
67°
51°
25
71°
53°
26
69°
51°
27
64°
45°
28
59°
47°
29
59°
46°
30
58°
43°
1
57°
45°
2
57°
48°
3
64°
47°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Alliston
Alliston's September 2026 forecast shows daily high temperatures ranging from 57° to 78°, with overnight lows between 43° and 62°. The average high for September is 69° with an average low of 51°. 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 Alliston. See also: October | November | December.
