S
M
T
W
T
F
S
30
78°
33°
31
83°
37°
1
73°
37°
2
57°
42°
3
52°
40°
4
61°
32°
5
63°
35°
6
61°
40°
7
69°
31°
8
78°
36°
9
85°
38°
10
86°
49°
11
79°
41°
12
78°
36°
13
62°
37°
14
70°
32°
15
76°
31°
16
71°
48°
17
67°
42°
18
75°
39°
19
76°
36°
20
81°
39°
21
82°
39°
22
79°
39°
23
77°
35°
24
79°
50°
25
63°
35°
26
66°
39°
27
71°
35°
28
70°
34°
29
78°
35°
30
79°
33°
1
76°
31°
2
70°
29°
3
76°
37°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Merrill
Merrill's September 2026 forecast shows daily high temperatures ranging from 63° to 79°, with overnight lows between 29° and 50°. The average high for September is 73° with an average low of 36°. 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 Merrill. See also: October | November | December.