S
M
T
W
T
F
S
30
71°
55°
31
76°
54°
1
66°
57°
2
70°
55°
3
68°
53°
4
70°
53°
5
70°
52°
6
74°
53°
7
70°
57°
8
74°
55°
9
78°
54°
10
71°
56°
11
67°
52°
12
66°
53°
13
60°
54°
14
67°
54°
15
68°
54°
16
74°
53°
17
77°
54°
18
69°
55°
19
63°
52°
20
70°
50°
21
67°
52°
22
68°
55°
23
67°
53°
24
63°
51°
25
62°
50°
26
65°
45°
27
67°
43°
28
66°
54°
29
65°
52°
30
67°
48°
1
66°
47°
2
64°
45°
3
65°
48°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Issaquah Plateau
Issaquah Plateau's September 2026 forecast shows daily high temperatures ranging from 64° to 67°, with overnight lows between 43° and 54°. The average high for September is 66° with an average low of 48°. 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 Issaquah Plateau. See also: October | November | December.
