S
M
T
W
T
F
S
29
48°
22°
30
42°
17°
1
39°
16°
2
41°
24°
3
46°
25°
4
41°
19°
5
39°
18°
6
39°
14°
7
37°
13°
8
39°
17°
9
46°
19°
10
47°
16°
11
46°
21°
12
48°
24°
13
49°
24°
14
43°
22°
15
42°
27°
16
44°
19°
17
41°
16°
18
40°
15°
19
41°
16°
20
40°
17°
21
42°
18°
22
42°
17°
23
43°
19°
24
43°
17°
25
42°
27°
26
44°
26°
27
49°
16°
28
43°
16°
29
41°
19°
30
43°
15°
31
41°
17°
1
41°
24°
2
45°
25°
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 37° to 49°, with overnight lows between 13° and 27°. The average high for December is 43° with an average low of 19°. 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.
