S
M
T
W
T
F
S
29
30°
3°
30
31°
10°
1
30°
3°
2
27°
2°
3
25°
3°
4
28°
4°
5
30°
3°
6
28°
-1°
7
26°
3°
8
27°
1°
9
27°
0°
10
28°
-1°
11
25°
1°
12
27°
5°
13
33°
7°
14
33°
6°
15
32°
3°
16
29°
11°
17
35°
12°
18
36°
7°
19
33°
10°
20
32°
9°
21
34°
10°
22
36°
9°
23
32°
9°
24
29°
12°
25
34°
13°
26
36°
11°
27
35°
12°
28
36°
9°
29
34°
4°
30
27°
0°
31
22°
-4°
1
22°
-2°
2
Hist. Avg.
27°
-3°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Keystone
Keystone's December 2026 forecast shows daily high temperatures ranging from 22° to 36°, with overnight lows between -4° and 13°. The average high for December is 30° with an average low of 5°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how December weather will actually feel in Keystone. See also: January | February | March.
