S
M
T
W
T
F
S
26
64°
39°
27
57°
42°
28
54°
36°
29
58°
36°
30
53°
38°
1
54°
35°
2
67°
32°
3
71°
48°
4
68°
47°
5
54°
37°
6
54°
32°
7
65°
37°
8
75°
39°
9
66°
45°
10
69°
38°
11
79°
38°
12
75°
54°
13
78°
47°
14
81°
54°
15
90°
54°
16
81°
53°
17
81°
59°
18
59°
46°
19
55°
41°
20
61°
36°
21
65°
46°
22
65°
49°
23
71°
47°
24
82°
52°
25
88°
60°
26
90°
65°
27
89°
63°
28
88°
64°
29
80°
65°
30
74°
62°
31
75°
60°
1
81°
59°
2
81°
58°
3
80°
61°
4
80°
62°
5
84°
61°
6
85°
62°
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 74° to 85°, with overnight lows between 58° and 62°. The average high for May is 80° with an average low of 61°. 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.
