S
M
T
W
T
F
S
29
31°
8°
30
28°
7°
1
29°
16°
2
32°
21°
3
36°
20°
4
31°
17°
5
29°
18°
6
30°
10°
7
28°
8°
8
32°
11°
9
36°
10°
10
35°
15°
11
39°
11°
12
38°
10°
13
39°
17°
14
33°
18°
15
29°
14°
16
35°
8°
17
31°
16°
18
30°
17°
19
32°
20°
20
34°
11°
21
35°
10°
22
28°
17°
23
33°
7°
24
33°
16°
25
30°
15°
26
34°
3°
27
34°
-1°
28
23°
11°
29
26°
4°
30
28°
6°
31
25°
15°
1
34°
20°
2
35°
8°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Boulder
Boulder's December 2026 forecast shows daily high temperatures ranging from 23° to 39°, with overnight lows between -1° and 21°. The average high for December is 32° with an average low of 12°. 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 Boulder. See also: January | February | March.
