S
M
T
W
T
F
S
26
66°
43°
27
68°
52°
28
66°
54°
29
55°
39°
30
57°
37°
1
48°
34°
2
55°
30°
3
66°
45°
4
84°
52°
5
59°
46°
6
61°
43°
7
61°
37°
8
66°
43°
9
77°
46°
10
63°
46°
11
55°
43°
12
75°
41°
13
55°
41°
14
64°
39°
15
73°
59°
16
79°
62°
17
87°
66°
18
84°
69°
19
75°
54°
20
63°
46°
21
61°
49°
22
70°
51°
23
77°
56°
24
73°
58°
25
75°
60°
26
73°
59°
27
75°
60°
28
76°
53°
29
76°
57°
30
71°
54°
31
70°
52°
1
71°
49°
2
70°
49°
3
70°
52°
4
73°
59°
5
80°
61°
6
81°
62°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Merrillville
Merrillville's May 2026 forecast shows daily high temperatures ranging from 61° to 87°, with overnight lows between 46° and 69°. The average high for May is 74° with an average low of 56°. 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 Merrillville. See also: June | July | August.