S
M
T
W
T
F
S
29
70°
48°
30
69°
41°
1
60°
35°
2
55°
34°
3
56°
39°
4
60°
46°
5
58°
39°
6
55°
35°
7
55°
35°
8
53°
32°
9
52°
32°
10
53°
33°
11
57°
34°
12
59°
39°
13
59°
41°
14
57°
36°
15
55°
34°
16
53°
37°
17
54°
34°
18
53°
30°
19
52°
29°
20
53°
31°
21
54°
32°
22
58°
32°
23
53°
30°
24
50°
29°
25
51°
30°
26
51°
32°
27
53°
32°
28
54°
33°
29
53°
30°
30
52°
32°
31
53°
29°
1
52°
29°
2
53°
38°
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 50° to 70°, with overnight lows between 29° and 48°. The average high for December is 55° with an average low of 34°. 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.
