S
M
T
W
T
F
S
30
73°
59°
31
75°
60°
1
74°
61°
2
71°
59°
3
75°
60°
4
79°
60°
5
80°
61°
6
78°
60°
7
73°
56°
8
77°
58°
9
77°
59°
10
70°
57°
11
68°
53°
12
67°
55°
13
67°
51°
14
68°
50°
15
69°
50°
16
73°
53°
17
71°
58°
18
66°
58°
19
66°
57°
20
67°
57°
21
66°
47°
22
68°
55°
23
68°
55°
24
72°
50°
25
74°
56°
26
72°
47°
27
63°
46°
28
60°
44°
29
61°
45°
30
60°
53°
1
61°
49°
2
61°
46°
3
64°
54°
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 60° to 80°, with overnight lows between 44° and 61°. The average high for September is 70° 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.
