S
M
T
W
T
F
S
30
87°
60°
31
84°
58°
1
82°
57°
2
82°
58°
3
83°
61°
4
85°
64°
5
88°
62°
6
87°
62°
7
86°
59°
8
81°
56°
9
80°
55°
10
80°
55°
11
81°
54°
12
79°
54°
13
78°
53°
14
77°
54°
15
78°
55°
16
78°
54°
17
80°
55°
18
80°
54°
19
82°
55°
20
Hist. Avg.
79°
56°
21
Hist. Avg.
79°
55°
22
Hist. Avg.
79°
55°
23
Hist. Avg.
78°
55°
24
Hist. Avg.
78°
54°
25
Hist. Avg.
78°
54°
26
Hist. Avg.
77°
54°
27
Hist. Avg.
77°
53°
28
Hist. Avg.
76°
53°
29
Hist. Avg.
76°
52°
30
Hist. Avg.
76°
52°
1
Hist. Avg.
75°
52°
2
Hist. Avg.
75°
51°
3
Hist. Avg.
75°
51°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Alton
Alton's September 2026 forecast shows daily high temperatures ranging from 77° to 88°, with overnight lows between 53° and 64°. The average high for September is 82° with an average low of 57°. 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 Alton. See also: October | November | December.
