S
M
T
W
T
F
S
26
61°
51°
27
71°
40°
28
64°
41°
29
66°
56°
30
73°
44°
1
68°
38°
2
61°
43°
3
65°
32°
4
79°
35°
5
82°
52°
6
73°
63°
7
65°
44°
8
72°
38°
9
78°
42°
10
86°
51°
11
63°
39°
12
74°
36°
13
79°
42°
14
68°
43°
15
76°
38°
16
87°
49°
17
93°
56°
18
96°
62°
19
96°
65°
20
96°
65°
21
91°
58°
22
59°
55°
23
61°
58°
24
73°
63°
25
79°
67°
26
77°
66°
27
79°
66°
28
84°
59°
29
78°
55°
30
70°
51°
31
71°
53°
1
73°
55°
2
77°
56°
3
77°
58°
4
78°
60°
5
81°
59°
6
77°
56°
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 61° to 84°, with overnight lows between 51° and 67°. The average high for May is 76° with an average low of 59°. 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.
