S
M
T
W
T
F
S
30
66°
50°
31
73°
47°
1
70°
50°
2
74°
50°
3
74°
49°
4
66°
46°
5
65°
45°
6
67°
47°
7
69°
48°
8
69°
43°
9
68°
42°
10
62°
38°
11
61°
39°
12
61°
45°
13
64°
42°
14
61°
36°
15
60°
37°
16
58°
37°
17
59°
35°
18
59°
34°
19
57°
34°
20
57°
35°
21
58°
36°
22
59°
39°
23
63°
42°
24
64°
41°
25
64°
37°
26
63°
39°
27
58°
36°
28
63°
32°
29
54°
31°
30
54°
40°
1
53°
39°
2
56°
41°
3
62°
29°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Casper Mountain
Casper Mountain's September 2026 forecast shows daily high temperatures ranging from 53° to 74°, with overnight lows between 29° and 50°. The average high for September is 63° with an average low of 40°. 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 Casper Mountain. See also: October | November | December.
