S
M
T
W
T
F
S
26
64°
32°
27
71°
35°
28
65°
37°
29
62°
42°
30
49°
42°
1
58°
38°
2
49°
39°
3
52°
37°
4
70°
38°
5
83°
52°
6
66°
48°
7
59°
38°
8
56°
31°
9
52°
32°
10
68°
45°
11
59°
42°
12
57°
33°
13
52°
47°
14
56°
47°
15
57°
46°
16
74°
54°
17
77°
51°
18
67°
54°
19
85°
62°
20
77°
49°
21
65°
46°
22
67°
50°
23
67°
48°
24
66°
47°
25
65°
49°
26
67°
47°
27
65°
48°
28
64°
46°
29
64°
47°
30
65°
52°
31
66°
52°
1
67°
51°
2
66°
50°
3
66°
48°
4
67°
46°
5
67°
53°
6
68°
53°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Alton
Alton's May 2026 forecast shows daily high temperatures ranging from 52° to 85°, with overnight lows between 46° and 62°. The average high for May is 67° with an average low of 50°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how May weather will actually feel in Alton. See also: June | July | August.
