S
M
T
W
T
F
S
30
79°
70°
31
86°
72°
1
86°
70°
2
82°
66°
3
84°
68°
4
88°
68°
5
84°
64°
6
79°
60°
7
79°
63°
8
86°
66°
9
84°
57°
10
79°
58°
11
81°
59°
12
83°
63°
13
77°
58°
14
75°
57°
15
78°
60°
16
77°
58°
17
78°
59°
18
76°
51°
19
79°
57°
20
80°
57°
21
75°
56°
22
77°
56°
23
78°
55°
24
78°
56°
25
77°
56°
26
77°
55°
27
78°
56°
28
77°
56°
29
76°
55°
30
76°
54°
1
74°
48°
2
63°
44°
3
64°
41°
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 63° to 86°, with overnight lows between 41° and 66°. The average high for September is 77° 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 September weather will actually feel in Decorah. See also: October | November | December.
