S
M
T
W
T
F
S
29
56°
39°
30
57°
40°
1
56°
35°
2
58°
25°
3
56°
24°
4
43°
22°
5
38°
21°
6
39°
22°
7
39°
23°
8
41°
25°
9
41°
24°
10
38°
21°
11
38°
25°
12
41°
27°
13
40°
21°
14
38°
19°
15
36°
20°
16
36°
28°
17
37°
34°
18
46°
35°
19
50°
34°
20
53°
32°
21
49°
36°
22
50°
35°
23
51°
31°
24
52°
24°
25
43°
25°
26
41°
31°
27
46°
35°
28
50°
35°
29
50°
33°
30
51°
29°
31
49°
24°
1
47°
22°
2
35°
23°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Alton
Alton's December 2026 forecast shows daily high temperatures ranging from 35° to 58°, with overnight lows between 19° and 40°. The average high for December is 45° with an average low of 28°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how December weather will actually feel in Alton. See also: January | February | March.
