S
M
T
W
T
F
S
26
80°
54°
27
83°
61°
28
67°
53°
29
66°
48°
30
65°
39°
1
64°
41°
2
64°
39°
3
75°
38°
4
79°
58°
5
65°
43°
6
60°
43°
7
66°
37°
8
75°
46°
9
81°
50°
10
72°
54°
11
74°
44°
12
77°
47°
13
76°
50°
14
74°
42°
15
81°
55°
16
84°
68°
17
82°
65°
18
84°
72°
19
73°
63°
20
63°
57°
21
73°
53°
22
66°
60°
23
76°
61°
24
79°
59°
25
78°
56°
26
74°
59°
27
85°
67°
28
78°
67°
29
78°
66°
30
77°
64°
31
83°
63°
1
85°
58°
2
81°
56°
3
80°
57°
4
79°
61°
5
80°
63°
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 77° to 85°, with overnight lows between 56° and 67°. The average high for May is 81° 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.
