S
M
T
W
T
F
S
30
84°
53°
31
83°
52°
1
83°
47°
2
73°
46°
3
70°
49°
4
72°
50°
5
81°
41°
6
72°
40°
7
69°
42°
8
70°
48°
9
74°
42°
10
71°
45°
11
70°
44°
12
78°
43°
13
70°
39°
14
66°
36°
15
66°
37°
16
66°
38°
17
68°
44°
18
74°
36°
19
67°
40°
20
66°
45°
21
75°
46°
22
76°
45°
23
74°
46°
24
76°
46°
25
76°
45°
26
74°
45°
27
75°
41°
28
69°
42°
29
62°
41°
30
62°
37°
1
65°
41°
2
62°
43°
3
57°
28°
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 57° to 84°, with overnight lows between 28° and 53°. The average high for September is 71° with an average low of 43°. 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.
