S
M
T
W
T
F
S
30
52°
36°
31
54°
39°
1
55°
39°
2
57°
41°
3
61°
41°
4
61°
43°
5
64°
45°
6
68°
45°
7
55°
45°
8
61°
41°
9
59°
41°
10
59°
37°
11
55°
39°
12
59°
45°
13
64°
45°
14
50°
37°
15
55°
37°
16
55°
37°
17
63°
48°
18
63°
44°
19
63°
42°
20
62°
37°
21
65°
40°
22
61°
39°
23
59°
36°
24
60°
38°
25
59°
40°
26
59°
39°
27
61°
38°
28
59°
39°
29
60°
38°
30
58°
27°
1
62°
32°
2
51°
29°
3
54°
31°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Keystone
Keystone's September 2026 forecast shows daily high temperatures ranging from 51° to 65°, with overnight lows between 27° and 48°. The average high for September is 60° 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 Keystone. See also: October | November | December.
