S
M
T
W
T
F
S
26
52°
37°
27
53°
39°
28
56°
44°
29
58°
45°
30
58°
45°
1
57°
44°
2
58°
45°
3
55°
42°
4
54°
40°
5
54°
39°
6
55°
41°
7
54°
40°
8
55°
40°
9
57°
42°
10
60°
47°
11
62°
47°
12
59°
45°
13
57°
41°
14
56°
45°
15
58°
44°
16
57°
42°
17
57°
42°
18
56°
41°
19
56°
42°
20
57°
43°
21
55°
43°
22
61°
47°
23
60°
45°
24
60°
48°
25
63°
49°
26
61°
50°
27
63°
50°
28
67°
49°
29
67°
50°
30
66°
45°
31
65°
45°
1
64°
48°
2
65°
46°
3
63°
44°
4
65°
50°
5
64°
51°
6
66°
46°
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 52° to 67°, with overnight lows between 37° and 51°. The average high for May is 59° with an average low of 44°. 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.
