S
M
T
W
T
F
S
29
37°
16°
30
37°
21°
1
36°
21°
2
37°
20°
3
37°
19°
4
34°
18°
5
34°
20°
6
33°
9°
7
30°
13°
8
38°
17°
9
40°
19°
10
37°
15°
11
22°
6°
12
25°
14°
13
30°
17°
14
31°
14°
15
34°
15°
16
36°
13°
17
35°
14°
18
34°
7°
19
30°
8°
20
27°
11°
21
27°
10°
22
35°
2°
23
27°
2°
24
22°
14°
25
29°
15°
26
34°
15°
27
34°
12°
28
33°
8°
29
32°
2°
30
30°
2°
31
28°
1°
1
24°
-1°
2
22°
3°
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 22° to 40°, 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.
