S
M
T
W
T
F
S
30
89°
66°
31
N/A
1
83°
54°
2
84°
56°
3
84°
57°
4
83°
59°
5
91°
65°
6
94°
64°
7
99°
65°
8
94°
62°
9
96°
65°
10
97°
64°
11
95°
63°
12
94°
64°
13
93°
63°
14
92°
59°
15
94°
64°
16
94°
63°
17
93°
63°
18
90°
61°
19
86°
61°
20
89°
60°
21
91°
62°
22
91°
62°
23
90°
61°
24
87°
59°
25
83°
54°
26
82°
55°
27
81°
54°
28
82°
55°
29
84°
57°
30
84°
59°
1
83°
57°
2
85°
58°
3
88°
60°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Simi Valley
Simi Valley's September 2026 forecast shows daily high temperatures ranging from 81° to 99°, with overnight lows between 54° and 65°. The average high for September is 89° with an average low of 60°. 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 Simi Valley. See also: October | November | December.
