S
M
T
W
T
F
S
26
63°
46°
27
78°
47°
28
74°
55°
29
63°
48°
30
58°
40°
1
53°
35°
2
51°
33°
3
62°
31°
4
74°
46°
5
70°
50°
6
59°
40°
7
59°
38°
8
69°
41°
9
72°
53°
10
66°
50°
11
68°
40°
12
72°
44°
13
66°
47°
14
63°
45°
15
69°
37°
16
77°
53°
17
85°
59°
18
89°
64°
19
89°
66°
20
67°
50°
21
68°
50°
22
62°
53°
23
76°
62°
24
72°
59°
25
78°
61°
26
79°
57°
27
74°
64°
28
78°
55°
29
79°
54°
30
74°
51°
31
77°
51°
1
76°
51°
2
76°
49°
3
77°
55°
4
80°
61°
5
79°
64°
6
80°
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 80°, with overnight lows between 49° and 64°. The average high for May is 78° with an average low of 55°. 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.
