S
M
T
W
T
F
S
26
74°
50°
27
66°
54°
28
70°
57°
29
64°
50°
30
63°
41°
1
57°
40°
2
55°
37°
3
63°
36°
4
77°
53°
5
68°
47°
6
57°
41°
7
61°
37°
8
70°
45°
9
76°
53°
10
71°
55°
11
71°
45°
12
76°
40°
13
71°
53°
14
66°
43°
15
71°
41°
16
77°
63°
17
82°
64°
18
82°
66°
19
83°
64°
20
69°
57°
21
68°
54°
22
63°
59°
23
74°
60°
24
78°
64°
25
76°
65°
26
75°
66°
27
79°
68°
28
81°
66°
29
80°
62°
30
76°
57°
31
77°
59°
1
75°
58°
2
74°
61°
3
76°
59°
4
78°
60°
5
79°
61°
6
77°
64°
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 81°, with overnight lows between 57° and 68°. The average high for May is 77° with an average low of 62°. 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.
