S
M
T
W
T
F
S
30
88°
72°
31
85°
68°
1
85°
67°
2
84°
62°
3
82°
62°
4
83°
63°
5
87°
69°
6
85°
71°
7
85°
70°
8
87°
68°
9
89°
69°
10
85°
67°
11
83°
66°
12
82°
65°
13
83°
66°
14
83°
66°
15
86°
65°
16
88°
69°
17
88°
68°
18
80°
62°
19
81°
63°
20
85°
65°
21
86°
67°
22
84°
67°
23
83°
66°
24
82°
64°
25
83°
66°
26
86°
67°
27
86°
68°
28
85°
67°
29
86°
66°
30
85°
67°
1
86°
66°
2
84°
66°
3
82°
64°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Fullerton
Fullerton's September 2026 forecast shows daily high temperatures ranging from 80° to 89°, with overnight lows between 62° and 71°. The average high for September is 85° with an average low of 66°. 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 Fullerton. See also: October | November | December.
