S
M
T
W
T
F
S
29
35°
14°
30
36°
18°
1
38°
23°
2
41°
24°
3
42°
21°
4
44°
23°
5
41°
19°
6
42°
23°
7
38°
19°
8
39°
20°
9
39°
17°
10
40°
14°
11
36°
9°
12
33°
9°
13
32°
10°
14
31°
7°
15
29°
7°
16
31°
8°
17
30°
7°
18
32°
6°
19
30°
8°
20
30°
11°
21
34°
13°
22
35°
18°
23
36°
22°
24
41°
20°
25
41°
19°
26
40°
17°
27
39°
18°
28
37°
18°
29
37°
18°
30
36°
12°
31
33°
5°
1
30°
5°
2
30°
15°
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 29° to 44°, with overnight lows between 5° and 24°. The average high for December is 36° with an average low of 15°. 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.
