S
M
T
W
T
F
S
29
68°
55°
30
69°
54°
1
69°
54°
2
64°
53°
3
68°
50°
4
61°
48°
5
61°
50°
6
63°
50°
7
62°
51°
8
61°
48°
9
60°
53°
10
61°
48°
11
60°
44°
12
59°
44°
13
58°
45°
14
60°
46°
15
61°
47°
16
60°
46°
17
60°
46°
18
61°
47°
19
62°
48°
20
62°
48°
21
64°
51°
22
64°
54°
23
62°
46°
24
65°
45°
25
60°
46°
26
60°
46°
27
61°
47°
28
62°
48°
29
64°
49°
30
64°
49°
31
65°
50°
1
64°
47°
2
65°
51°
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 69°, with overnight lows between 44° and 55°. The average high for December is 63° 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.
