S
M
T
W
T
F
S
30
93°
68°
31
88°
59°
1
85°
56°
2
84°
54°
3
82°
56°
4
83°
59°
5
89°
56°
6
70°
65°
7
93°
65°
8
88°
67°
9
105°
67°
10
101°
74°
11
95°
71°
12
90°
66°
13
88°
63°
14
89°
60°
15
82°
61°
16
80°
66°
17
81°
61°
18
82°
54°
19
86°
52°
20
86°
59°
21
81°
57°
22
86°
60°
23
96°
64°
24
96°
64°
25
95°
65°
26
91°
66°
27
91°
64°
28
89°
64°
29
86°
62°
30
86°
64°
1
89°
65°
2
84°
59°
3
85°
62°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Castaic
Castaic's September 2026 forecast shows daily high temperatures ranging from 81° to 96°, with overnight lows between 57° and 66°. The average high for September is 89° with an average low of 63°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how September weather will actually feel in Castaic. See also: October | November | December.
