S
M
T
W
T
F
S
29
55°
39°
30
54°
38°
1
54°
44°
2
56°
41°
3
57°
44°
4
59°
39°
5
57°
36°
6
53°
40°
7
57°
41°
8
60°
40°
9
60°
40°
10
59°
41°
11
59°
42°
12
60°
42°
13
61°
41°
14
60°
42°
15
59°
41°
16
59°
42°
17
58°
41°
18
59°
39°
19
59°
42°
20
58°
37°
21
51°
33°
22
50°
35°
23
48°
38°
24
50°
35°
25
49°
34°
26
48°
33°
27
50°
32°
28
49°
34°
29
51°
35°
30
51°
42°
31
52°
37°
1
54°
39°
2
52°
41°
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 48° to 61°, with overnight lows between 32° and 44°. The average high for December is 55° with an average low of 39°. 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.
