S
M
T
W
T
F
S
26
78°
52°
27
78°
60°
28
65°
55°
29
63°
44°
30
66°
40°
1
62°
43°
2
61°
43°
3
75°
54°
4
81°
57°
5
60°
46°
6
58°
44°
7
62°
47°
8
64°
46°
9
69°
49°
10
70°
51°
11
66°
48°
12
70°
52°
13
75°
55°
14
74°
53°
15
76°
56°
16
75°
55°
17
77°
59°
18
74°
60°
19
78°
59°
20
73°
54°
21
76°
53°
22
70°
52°
23
70°
52°
24
71°
53°
25
70°
54°
26
70°
53°
27
72°
54°
28
73°
58°
29
74°
58°
30
77°
64°
31
74°
61°
1
75°
56°
2
76°
58°
3
77°
61°
4
78°
65°
5
80°
66°
6
78°
66°
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 58° to 81°, with overnight lows between 44° and 66°. The average high for May is 73° with an average low of 55°. 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.
