S
M
T
W
T
F
S
29
49°
22°
30
45°
29°
1
43°
24°
2
45°
25°
3
43°
28°
4
45°
27°
5
47°
26°
6
50°
22°
7
45°
19°
8
50°
24°
9
51°
27°
10
47°
19°
11
40°
13°
12
38°
15°
13
41°
19°
14
47°
18°
15
45°
26°
16
51°
25°
17
55°
26°
18
49°
24°
19
49°
24°
20
47°
23°
21
42°
23°
22
53°
15°
23
43°
11°
24
38°
15°
25
39°
21°
26
46°
24°
27
48°
25°
28
50°
22°
29
46°
24°
30
49°
26°
31
48°
18°
1
43°
13°
2
41°
15°
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 38° to 55°, with overnight lows between 11° and 29°. The average high for December is 46° 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.
