S
M
T
W
T
F
S
26
92°
77°
27
92°
77°
28
96°
80°
29
96°
76°
30
94°
78°
1
86°
67°
2
77°
62°
3
86°
62°
4
85°
66°
5
94°
77°
6
101°
81°
7
84°
73°
8
90°
72°
9
93°
71°
10
95°
75°
11
90°
70°
12
92°
70°
13
93°
70°
14
95°
68°
15
93°
72°
16
94°
76°
17
93°
81°
18
97°
79°
19
96°
81°
20
93°
70°
21
87°
71°
22
95°
79°
23
88°
75°
24
87°
73°
25
89°
75°
26
89°
76°
27
91°
77°
28
95°
75°
29
97°
75°
30
96°
76°
31
93°
75°
1
92°
74°
2
93°
75°
3
92°
76°
4
95°
75°
5
92°
77°
6
93°
76°
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 87° to 97°, with overnight lows between 73° and 79°. The average high for May is 92° with an average low of 76°. 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.
