S
M
T
W
T
F
S
30
73°
54°
31
80°
52°
1
72°
52°
2
73°
53°
3
71°
59°
4
76°
58°
5
79°
58°
6
79°
59°
7
70°
51°
8
68°
51°
9
69°
52°
10
70°
56°
11
76°
58°
12
76°
58°
13
67°
57°
14
69°
60°
15
67°
58°
16
67°
57°
17
68°
53°
18
67°
57°
19
66°
52°
20
67°
48°
21
68°
49°
22
66°
50°
23
66°
50°
24
69°
53°
25
72°
55°
26
70°
53°
27
67°
48°
28
Hist. Avg.
68°
51°
29
Hist. Avg.
67°
51°
30
Hist. Avg.
67°
51°
1
Hist. Avg.
66°
50°
2
Hist. Avg.
66°
50°
3
Hist. Avg.
65°
50°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in SeaTac
SeaTac's September 2026 forecast shows daily high temperatures ranging from 66° to 80°, with overnight lows between 48° and 60°. The average high for September is 71° 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 SeaTac. See also: October | November | December.
