S
M
T
W
T
F
S
29
66°
40°
30
66°
41°
1
65°
42°
2
65°
43°
3
67°
44°
4
70°
45°
5
71°
39°
6
64°
43°
7
66°
45°
8
71°
44°
9
71°
44°
10
70°
46°
11
70°
45°
12
71°
46°
13
71°
44°
14
70°
44°
15
70°
45°
16
69°
46°
17
70°
46°
18
71°
45°
19
71°
42°
20
70°
42°
21
63°
37°
22
62°
37°
23
61°
41°
24
64°
42°
25
65°
44°
26
63°
42°
27
63°
41°
28
64°
40°
29
64°
41°
30
65°
44°
31
64°
42°
1
65°
43°
2
66°
44°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Simi Valley
Simi Valley's December 2026 forecast shows daily high temperatures ranging from 61° to 71°, with overnight lows between 37° and 46°. The average high for December is 67° with an average low of 43°. 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 Simi Valley. See also: January | February | March.
