S
M
T
W
T
F
S
30
90°
62°
31
91°
61°
1
91°
62°
2
90°
62°
3
89°
61°
4
89°
62°
5
88°
60°
6
89°
52°
7
79°
51°
8
79°
56°
9
78°
58°
10
77°
57°
11
81°
58°
12
86°
59°
13
86°
47°
14
85°
47°
15
75°
46°
16
73°
47°
17
75°
51°
18
79°
51°
19
79°
46°
20
74°
47°
21
74°
53°
22
79°
53°
23
82°
54°
24
82°
55°
25
81°
54°
26
83°
54°
27
81°
53°
28
79°
49°
29
77°
50°
30
76°
48°
1
74°
47°
2
77°
50°
3
69°
38°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Grinnell
Grinnell's September 2026 forecast shows daily high temperatures ranging from 69° to 91°, with overnight lows between 38° and 62°. The average high for September is 81° with an average low of 53°. 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 Grinnell. See also: October | November | December.
