S
M
T
W
T
F
S
29
43°
28°
30
46°
30°
1
45°
29°
2
43°
30°
3
46°
28°
4
44°
27°
5
44°
27°
6
41°
28°
7
44°
26°
8
38°
25°
9
35°
26°
10
36°
26°
11
36°
25°
12
37°
23°
13
37°
18°
14
38°
14°
15
33°
15°
16
29°
16°
17
31°
15°
18
30°
22°
19
34°
21°
20
37°
20°
21
35°
16°
22
34°
16°
23
31°
7°
24
31°
16°
25
28°
13°
26
31°
7°
27
27°
5°
28
23°
6°
29
27°
5°
30
25°
10°
31
26°
19°
1
38°
16°
2
37°
9°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Thornton
Thornton's December 2026 forecast shows daily high temperatures ranging from 23° to 46°, with overnight lows between 5° and 30°. The average high for December is 35° 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 Thornton. See also: January | February | March.
