S
M
T
W
T
F
S
26
57°
27°
27
50°
36°
28
51°
31°
29
52°
28°
30
51°
29°
1
57°
24°
2
72°
35°
3
75°
37°
4
63°
31°
5
44°
26°
6
45°
31°
7
63°
26°
8
68°
32°
9
60°
37°
10
58°
38°
11
71°
37°
12
73°
44°
13
77°
36°
14
84°
61°
15
80°
51°
16
57°
39°
17
52°
42°
18
51°
39°
19
51°
33°
20
64°
45°
21
68°
48°
22
71°
53°
23
68°
52°
24
74°
51°
25
73°
54°
26
78°
58°
27
77°
56°
28
78°
56°
29
73°
51°
30
71°
56°
31
76°
58°
1
74°
57°
2
69°
57°
3
73°
55°
4
74°
58°
5
76°
59°
6
69°
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 51° to 78°, with overnight lows between 33° and 59°. The average high for May is 69° with an average low of 51°. 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.
