S
M
T
W
T
F
S
30
81°
56°
31
76°
66°
1
86°
69°
2
74°
69°
3
86°
69°
4
85°
60°
5
81°
58°
6
76°
59°
7
78°
59°
8
77°
58°
9
74°
59°
10
78°
59°
11
77°
58°
12
77°
57°
13
78°
56°
14
77°
57°
15
74°
57°
16
74°
59°
17
76°
52°
18
72°
50°
19
71°
50°
20
72°
54°
21
77°
58°
22
79°
58°
23
80°
58°
24
79°
56°
25
77°
54°
26
77°
55°
27
78°
56°
28
77°
56°
29
78°
52°
30
70°
49°
1
67°
48°
2
69°
52°
3
75°
54°
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 67° to 86°, with overnight lows between 48° and 69°. The average high for September is 77° 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 September weather will actually feel in Fullerton. See also: October | November | December.
