S
M
T
W
T
F
S
26
63°
51°
27
64°
49°
28
75°
42°
29
78°
46°
30
81°
47°
1
82°
51°
2
86°
52°
3
71°
49°
4
66°
49°
5
66°
48°
6
79°
56°
7
88°
61°
8
89°
59°
9
89°
60°
10
90°
61°
11
92°
62°
12
86°
58°
13
87°
60°
14
85°
59°
15
81°
54°
16
80°
57°
17
83°
58°
18
84°
58°
19
84°
57°
20
83°
58°
21
84°
58°
22
84°
57°
23
86°
59°
24
86°
59°
25
85°
58°
26
85°
59°
27
84°
58°
28
78°
58°
29
79°
57°
30
78°
57°
31
79°
58°
1
80°
59°
2
83°
58°
3
82°
59°
4
81°
58°
5
81°
57°
6
80°
55°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Castaic
Castaic's May 2026 forecast shows daily high temperatures ranging from 66° to 92°, with overnight lows between 48° and 62°. The average high for May is 82° with an average low of 57°. 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 Castaic. See also: June | July | August.
