S
M
T
W
T
F
S
30
79°
58°
31
82°
62°
1
85°
55°
2
82°
56°
3
78°
55°
4
79°
56°
5
79°
63°
6
83°
61°
7
85°
60°
8
78°
61°
9
77°
61°
10
80°
60°
11
79°
58°
12
80°
60°
13
78°
58°
14
75°
53°
15
75°
52°
16
74°
51°
17
74°
53°
18
75°
57°
19
77°
57°
20
78°
58°
21
79°
54°
22
73°
50°
23
72°
55°
24
71°
57°
25
78°
50°
26
69°
54°
27
70°
51°
28
Hist. Avg.
73°
51°
29
Hist. Avg.
72°
50°
30
Hist. Avg.
72°
50°
1
Hist. Avg.
71°
49°
2
Hist. Avg.
71°
49°
3
Hist. Avg.
71°
49°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Fullerton
Fullerton's September 2026 forecast shows daily high temperatures ranging from 69° to 85°, with overnight lows between 50° and 63°. The average high for September is 77° with an average low of 56°. 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.
