S
M
T
W
T
F
S
26
70°
62°
27
70°
63°
28
71°
64°
29
70°
63°
30
72°
64°
31
74°
66°
1
76°
68°
2
76°
68°
3
75°
67°
4
75°
67°
5
74°
66°
6
73°
66°
7
73°
67°
8
74°
66°
9
74°
67°
10
74°
66°
11
74°
63°
12
74°
63°
13
73°
64°
14
72°
69°
15
73°
68°
16
75°
69°
17
77°
69°
18
77°
68°
19
75°
69°
20
77°
69°
21
77°
68°
22
76°
68°
23
77°
67°
24
76°
68°
25
76°
69°
26
75°
68°
27
76°
68°
28
75°
66°
29
74°
65°
30
72°
67°
31
73°
65°
1
73°
64°
2
74°
63°
3
72°
61°
4
70°
62°
5
70°
62°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
August Weather in Costa Mesa
Costa Mesa's August 2026 forecast shows daily high temperatures ranging from 70° to 77°, with overnight lows between 61° and 69°. The average high for August is 74° with an average low of 66°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how August weather will actually feel in Costa Mesa. See also: September | October | November.
