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