S
M
T
W
T
F
S
30
81°
68°
31
93°
72°
1
97°
75°
2
96°
72°
3
91°
71°
4
90°
72°
5
86°
65°
6
80°
62°
7
81°
62°
8
80°
61°
9
81°
65°
10
77°
58°
11
74°
55°
12
76°
54°
13
75°
57°
14
78°
54°
15
79°
59°
16
79°
60°
17
78°
59°
18
79°
59°
19
80°
60°
20
80°
60°
21
79°
59°
22
80°
59°
23
79°
58°
24
79°
59°
25
78°
58°
26
79°
56°
27
78°
57°
28
78°
57°
29
77°
56°
30
76°
55°
1
76°
55°
2
75°
54°
3
76°
54°
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 74° to 96°, with overnight lows between 54° and 72°. The average high for September is 80° with an average low of 59°. 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.
