S
M
T
W
T
F
S
30
81°
61°
31
81°
60°
1
83°
61°
2
82°
61°
3
77°
60°
4
77°
61°
5
79°
60°
6
78°
61°
7
76°
61°
8
77°
60°
9
76°
60°
10
77°
61°
11
78°
59°
12
77°
58°
13
80°
57°
14
77°
57°
15
78°
58°
16
78°
59°
17
75°
60°
18
75°
58°
19
81°
60°
20
81°
61°
21
75°
54°
22
75°
55°
23
78°
56°
24
81°
59°
25
80°
58°
26
81°
57°
27
81°
54°
28
74°
53°
29
73°
53°
30
73°
54°
1
77°
54°
2
79°
57°
3
79°
58°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Cupertino
Cupertino's September 2026 forecast shows daily high temperatures ranging from 73° to 83°, with overnight lows between 53° and 61°. The average high for September is 78° with an average low of 58°. 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 Cupertino. See also: October | November | December.
