S
M
T
W
T
F
S
26
57°
45°
27
57°
46°
28
55°
48°
29
57°
48°
30
57°
48°
1
54°
48°
2
54°
48°
3
55°
48°
4
59°
50°
5
61°
50°
6
59°
50°
7
59°
48°
8
59°
46°
9
57°
48°
10
59°
50°
11
64°
50°
12
66°
50°
13
63°
48°
14
61°
48°
15
59°
48°
16
57°
46°
17
59°
46°
18
62°
45°
19
62°
48°
20
60°
46°
21
66°
49°
22
61°
49°
23
63°
47°
24
62°
46°
25
58°
44°
26
60°
46°
27
61°
47°
28
61°
46°
29
62°
46°
30
63°
47°
31
74°
55°
1
68°
54°
2
68°
55°
3
67°
54°
4
69°
54°
5
69°
53°
6
68°
55°
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 58° to 74°, with overnight lows between 44° and 55°. The average high for May is 64° with an average low of 49°. 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.
