S
M
T
W
T
F
S
26
54°
34°
27
54°
36°
28
59°
39°
29
63°
44°
30
66°
45°
1
67°
43°
2
57°
40°
3
57°
38°
4
58°
35°
5
58°
44°
6
59°
46°
7
65°
47°
8
67°
43°
9
58°
40°
10
60°
42°
11
60°
45°
12
61°
44°
13
63°
47°
14
62°
46°
15
65°
50°
16
70°
50°
17
65°
49°
18
64°
44°
19
62°
44°
20
64°
51°
21
67°
51°
22
65°
42°
23
69°
44°
24
72°
46°
25
71°
47°
26
73°
48°
27
76°
50°
28
76°
54°
29
77°
50°
30
77°
51°
31
70°
52°
1
73°
53°
2
78°
46°
3
71°
56°
4
78°
58°
5
79°
58°
6
80°
59°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Allegan
Allegan's May 2026 forecast shows daily high temperatures ranging from 54° to 80°, with overnight lows between 34° and 59°. The average high for May is 66° with an average low of 46°. 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 Allegan. See also: June | July | August.