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°
57°
11
67°
56°
12
67°
55°
13
70°
55°
14
69°
54°
15
76°
55°
16
79°
57°
17
84°
58°
18
81°
57°
19
71°
55°
20
69°
54°
21
71°
55°
22
70°
53°
23
72°
55°
24
68°
53°
25
63°
56°
26
64°
54°
27
63°
50°
28
62°
49°
29
62°
47°
30
61°
47°
1
62°
55°
2
64°
54°
3
62°
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 61° to 84°, with overnight lows between 47° and 58°. The average high for September is 69° with an average low of 54°. 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.
