S
M
T
W
T
F
S
30
85°
61°
31
86°
62°
1
88°
63°
2
87°
50°
3
84°
51°
4
75°
57°
5
84°
55°
6
80°
61°
7
84°
61°
8
86°
63°
9
86°
62°
10
84°
60°
11
85°
48°
12
81°
47°
13
68°
47°
14
67°
48°
15
72°
56°
16
72°
56°
17
69°
55°
18
77°
53°
19
69°
52°
20
66°
54°
21
68°
53°
22
65°
51°
23
65°
49°
24
67°
52°
25
74°
52°
26
75°
43°
27
74°
44°
28
63°
49°
29
72°
40°
30
61°
37°
1
57°
37°
2
58°
35°
3
57°
37°
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 57° to 88°, with overnight lows between 35° and 63°. The average high for September is 74° with an average low of 51°. 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.
