S
M
T
W
T
F
S
30
74°
50°
31
71°
47°
1
68°
49°
2
68°
46°
3
69°
47°
4
69°
47°
5
68°
48°
6
68°
51°
7
69°
55°
8
68°
48°
9
68°
48°
10
69°
47°
11
68°
50°
12
67°
49°
13
68°
50°
14
67°
49°
15
66°
48°
16
67°
45°
17
66°
44°
18
67°
45°
19
72°
48°
20
Hist. Avg.
67°
47°
21
Hist. Avg.
67°
47°
22
Hist. Avg.
66°
47°
23
Hist. Avg.
66°
46°
24
Hist. Avg.
66°
46°
25
Hist. Avg.
65°
46°
26
Hist. Avg.
65°
45°
27
Hist. Avg.
65°
45°
28
Hist. Avg.
64°
45°
29
Hist. Avg.
64°
44°
30
Hist. Avg.
64°
44°
1
Hist. Avg.
63°
44°
2
Hist. Avg.
63°
43°
3
Hist. Avg.
62°
43°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Alliston
Alliston's September 2026 forecast shows daily high temperatures ranging from 66° to 74°, with overnight lows between 44° and 55°. The average high for September is 68° with an average low of 48°. 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.
