S
M
T
W
T
F
S
30
77°
56°
31
80°
60°
1
78°
53°
2
82°
52°
3
74°
51°
4
73°
51°
5
73°
52°
6
75°
57°
7
81°
60°
8
84°
60°
9
80°
51°
10
74°
52°
11
74°
58°
12
75°
51°
13
79°
49°
14
73°
47°
15
71°
49°
16
73°
54°
17
75°
50°
18
79°
46°
19
71°
53°
20
73°
47°
21
72°
55°
22
70°
55°
23
79°
56°
24
79°
55°
25
78°
55°
26
78°
54°
27
79°
54°
28
78°
53°
29
76°
53°
30
77°
54°
1
78°
46°
2
77°
42°
3
75°
42°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Decorah
Decorah's September 2026 forecast shows daily high temperatures ranging from 70° to 84°, with overnight lows between 42° and 60°. The average high for September is 76° with an average low of 52°. 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 Decorah. See also: October | November | December.
