S
M
T
W
T
F
S
30
87°
53°
31
88°
52°
1
87°
53°
2
84°
53°
3
87°
50°
4
80°
51°
5
84°
55°
6
87°
55°
7
87°
52°
8
81°
54°
9
84°
54°
10
85°
53°
11
78°
53°
12
84°
51°
13
82°
52°
14
83°
53°
15
85°
53°
16
84°
52°
17
Hist. Avg.
77°
47°
18
Hist. Avg.
76°
46°
19
Hist. Avg.
76°
46°
20
Hist. Avg.
75°
46°
21
Hist. Avg.
75°
45°
22
Hist. Avg.
74°
45°
23
Hist. Avg.
74°
44°
24
Hist. Avg.
74°
44°
25
Hist. Avg.
73°
43°
26
Hist. Avg.
73°
43°
27
Hist. Avg.
72°
42°
28
Hist. Avg.
72°
42°
29
Hist. Avg.
71°
42°
30
Hist. Avg.
71°
41°
1
Hist. Avg.
70°
41°
2
Hist. Avg.
70°
40°
3
Hist. Avg.
70°
40°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Sunnyvale
Sunnyvale's September 2026 forecast shows daily high temperatures ranging from 78° to 88°, with overnight lows between 50° and 55°. The average high for September is 84° with an average low of 53°. 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 Sunnyvale. See also: October | November | December.
