S
M
T
W
T
F
S
30
81°
68°
31
93°
72°
1
97°
75°
2
97°
74°
3
91°
71°
4
90°
72°
5
82°
65°
6
83°
62°
7
81°
62°
8
80°
61°
9
86°
65°
10
77°
58°
11
76°
60°
12
79°
57°
13
76°
57°
14
75°
56°
15
76°
54°
16
79°
60°
17
78°
59°
18
73°
58°
19
76°
59°
20
77°
59°
21
77°
58°
22
75°
56°
23
72°
53°
24
72°
54°
25
76°
57°
26
76°
51°
27
66°
47°
28
65°
46°
29
66°
47°
30
65°
45°
1
63°
44°
2
66°
51°
3
68°
52°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Merrillville
Merrillville's September 2026 forecast shows daily high temperatures ranging from 63° to 97°, with overnight lows between 44° and 74°. The average high for September is 76° with an average low of 57°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how September weather will actually feel in Merrillville. See also: October | November | December.
