S
M
T
W
T
F
S
26
78°
69°
27
76°
70°
28
77°
69°
29
78°
70°
30
78°
69°
31
78°
70°
1
76°
69°
2
77°
70°
3
76°
69°
4
77°
69°
5
77°
67°
6
76°
68°
7
78°
68°
8
78°
68°
9
78°
68°
10
78°
68°
11
77°
68°
12
77°
67°
13
81°
68°
14
81°
66°
15
78°
68°
16
80°
67°
17
80°
68°
18
75°
68°
19
77°
69°
20
76°
66°
21
73°
68°
22
72°
67°
23
74°
67°
24
76°
68°
25
75°
66°
26
74°
65°
27
77°
69°
28
78°
69°
29
73°
69°
30
74°
68°
31
75°
69°
1
74°
67°
2
73°
66°
3
74°
67°
4
72°
64°
5
72°
66°
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 72° to 81°, with overnight lows between 64° and 69°. The average high for August is 76° with an average low of 67°. 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.
