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
72°
53°
19
70°
52°
20
69°
52°
21
70°
55°
22
68°
51°
23
67°
52°
24
68°
53°
25
67°
52°
26
66°
53°
27
68°
52°
28
66°
50°
29
67°
52°
30
67°
51°
1
66°
50°
2
63°
53°
3
63°
48°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Seattle
Seattle's September 2026 forecast shows daily high temperatures ranging from 63° to 72°, with overnight lows between 48° and 55°. The average high for September is 67° with an average low of 52°. 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 Seattle. See also: October | November | December.
