S
M
T
W
T
F
S
29
38°
31°
30
37°
28°
1
38°
26°
2
37°
30°
3
37°
29°
4
39°
25°
5
39°
28°
6
41°
25°
7
36°
28°
8
38°
28°
9
40°
27°
10
38°
27°
11
34°
12°
12
31°
14°
13
34°
16°
14
36°
17°
15
38°
19°
16
39°
20°
17
40°
25°
18
40°
27°
19
39°
28°
20
38°
29°
21
40°
21°
22
42°
15°
23
39°
13°
24
30°
14°
25
31°
18°
26
36°
25°
27
41°
25°
28
38°
26°
29
37°
27°
30
38°
22°
31
38°
14°
1
33°
13°
2
33°
14°
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 30° to 42°, with overnight lows between 12° and 31°. The average high for December is 37° with an average low of 22°. 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.
