S
M
T
W
T
F
S
29
62°
46°
30
62°
43°
1
61°
47°
2
61°
48°
3
60°
48°
4
57°
47°
5
58°
46°
6
58°
44°
7
57°
47°
8
56°
45°
9
58°
46°
10
57°
43°
11
55°
46°
12
57°
46°
13
59°
47°
14
59°
43°
15
58°
43°
16
57°
45°
17
59°
42°
18
53°
41°
19
53°
38°
20
52°
37°
21
52°
37°
22
53°
42°
23
53°
37°
24
54°
37°
25
51°
38°
26
52°
36°
27
51°
35°
28
52°
38°
29
53°
40°
30
54°
41°
31
58°
40°
1
55°
37°
2
53°
37°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Mill Valley
Mill Valley's December 2026 forecast shows daily high temperatures ranging from 51° to 62°, with overnight lows between 35° and 48°. The average high for December is 56° with an average low of 42°. 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 Mill Valley. See also: January | February | March.
