S
M
T
W
T
F
S
29
42°
19°
30
41°
20°
1
39°
22°
2
40°
20°
3
40°
22°
4
39°
18°
5
39°
9°
6
35°
7°
7
31°
10°
8
30°
9°
9
33°
9°
10
31°
10°
11
31°
12°
12
32°
8°
13
37°
7°
14
30°
6°
15
29°
9°
16
29°
7°
17
33°
21°
18
36°
15°
19
39°
14°
20
38°
6°
21
34°
4°
22
29°
5°
23
28°
10°
24
29°
18°
25
35°
8°
26
35°
6°
27
30°
3°
28
29°
5°
29
29°
13°
30
33°
6°
31
39°
4°
1
30°
5°
2
28°
14°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Roundup
Roundup's December 2026 forecast shows daily high temperatures ranging from 28° to 42°, with overnight lows between 3° and 22°. The average high for December is 34° with an average low of 11°. 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 Roundup. See also: January | February | March.
