S
M
T
W
T
F
S
26
45°
31°
27
52°
30°
28
55°
21°
29
57°
18°
30
57°
21°
1
55°
16°
2
62°
18°
3
66°
21°
4
59°
28°
5
57°
15°
6
61°
28°
7
70°
21°
8
74°
30°
9
72°
29°
10
73°
24°
11
79°
23°
12
81°
32°
13
78°
36°
14
74°
26°
15
75°
34°
16
71°
31°
17
64°
26°
18
45°
25°
19
56°
16°
20
63°
19°
21
68°
26°
22
62°
33°
23
72°
34°
24
76°
31°
25
70°
40°
26
69°
45°
27
65°
35°
28
64°
33°
29
63°
36°
30
74°
40°
31
79°
42°
1
79°
45°
2
80°
44°
3
80°
43°
4
74°
44°
5
76°
43°
6
76°
41°
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 63° to 80°, with overnight lows between 33° and 45°. The average high for May is 73° with an average low of 41°. 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.
