S
M
T
W
T
F
S
26
78°
61°
27
76°
61°
28
78°
60°
29
77°
59°
30
76°
58°
31
76°
57°
1
76°
58°
2
75°
59°
3
76°
58°
4
78°
60°
5
79°
62°
6
79°
61°
7
78°
61°
8
79°
62°
9
80°
62°
10
80°
61°
11
79°
58°
12
78°
57°
13
78°
55°
14
74°
55°
15
74°
58°
16
76°
58°
17
79°
60°
18
80°
60°
19
81°
59°
20
80°
60°
21
80°
60°
22
78°
61°
23
79°
57°
24
75°
55°
25
76°
56°
26
74°
55°
27
75°
55°
28
75°
56°
29
76°
55°
30
78°
58°
31
81°
59°
1
81°
59°
2
82°
58°
3
81°
58°
4
81°
61°
5
80°
60°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
August Weather in Castro Valley
Castro Valley's August 2026 forecast shows daily high temperatures ranging from 74° to 82°, with overnight lows between 55° and 62°. The average high for August is 78° with an average low of 59°. 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 Castro Valley. See also: September | October | November.
