S
M
T
W
T
F
S
26
64°
39°
27
63°
48°
28
57°
45°
29
63°
43°
30
70°
46°
1
68°
43°
2
63°
45°
3
55°
50°
4
55°
43°
5
54°
37°
6
54°
43°
7
59°
39°
8
63°
43°
9
61°
46°
10
55°
41°
11
54°
37°
12
54°
36°
13
54°
43°
14
55°
41°
15
54°
43°
16
52°
41°
17
57°
45°
18
57°
45°
19
61°
50°
20
61°
52°
21
68°
52°
22
79°
57°
23
72°
52°
24
77°
48°
25
88°
54°
26
88°
59°
27
N/A
28
84°
55°
29
74°
52°
30
75°
56°
31
68°
54°
1
68°
55°
2
66°
51°
3
65°
52°
4
64°
51°
5
63°
50°
6
64°
49°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
May Weather in Alton
Alton's May 2026 forecast shows daily high temperatures ranging from 63° to 84°, with overnight lows between 49° and 56°. The average high for May is 69° with an average low of 53°. 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.
