S
M
T
W
T
F
S
29
66°
55°
30
62°
50°
1
61°
48°
2
62°
49°
3
61°
48°
4
61°
55°
5
61°
55°
6
66°
51°
7
65°
47°
8
62°
49°
9
63°
50°
10
62°
53°
11
66°
53°
12
68°
50°
13
67°
45°
14
61°
43°
15
58°
46°
16
59°
45°
17
59°
45°
18
58°
47°
19
61°
51°
20
61°
51°
21
62°
47°
22
62°
52°
23
63°
46°
24
60°
47°
25
61°
48°
26
62°
47°
27
61°
46°
28
62°
48°
29
63°
54°
30
65°
50°
31
67°
47°
1
66°
47°
2
63°
48°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Costa Mesa
Costa Mesa's December 2026 forecast shows daily high temperatures ranging from 58° to 68°, with overnight lows between 43° and 55°. The average high for December is 62° with an average low of 49°. 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 Costa Mesa. See also: January | February | March.
