S
M
T
W
T
F
S
30
77°
62°
31
65°
54°
1
73°
54°
2
77°
51°
3
68°
54°
4
77°
51°
5
84°
58°
6
76°
60°
7
69°
61°
8
65°
55°
9
73°
49°
10
82°
46°
11
66°
49°
12
59°
39°
13
62°
34°
14
60°
39°
15
60°
37°
16
54°
37°
17
64°
34°
18
62°
43°
19
69°
50°
20
58°
43°
21
67°
38°
22
67°
34°
23
60°
50°
24
70°
50°
25
66°
46°
26
65°
49°
27
63°
39°
28
63°
41°
29
68°
42°
30
59°
36°
1
54°
33°
2
57°
39°
3
55°
34°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Rapid City
Rapid City's September 2026 forecast shows daily high temperatures ranging from 54° to 68°, with overnight lows between 33° and 42°. The average high for September is 59° with an average low of 37°. 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 Rapid City. See also: October | November | December.
