S
M
T
W
T
F
S
26
64°
50°
27
67°
46°
28
74°
47°
29
70°
49°
30
74°
51°
1
70°
52°
2
57°
53°
3
63°
53°
4
66°
52°
5
59°
51°
6
67°
53°
7
74°
52°
8
67°
52°
9
66°
52°
10
74°
52°
11
87°
46°
12
69°
51°
13
64°
54°
14
75°
50°
15
75°
51°
16
72°
48°
17
78°
57°
18
88°
55°
19
82°
57°
20
81°
55°
21
72°
55°
22
68°
56°
23
70°
53°
24
72°
53°
25
71°
54°
26
72°
55°
27
71°
52°
28
67°
51°
29
66°
50°
30
67°
50°
31
72°
52°
1
73°
54°
2
75°
57°
3
75°
55°
4
67°
52°
5
71°
55°
6
75°
53°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Castro Valley
Castro Valley's May 2026 forecast shows daily high temperatures ranging from 66° to 88°, with overnight lows between 48° and 57°. The average high for May is 73° with an average low of 53°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how May weather will actually feel in Castro Valley. See also: June | July | August.
