S
M
T
W
T
F
S
30
66°
50°
31
74°
47°
1
68°
51°
2
71°
60°
3
68°
49°
4
66°
47°
5
70°
50°
6
70°
44°
7
67°
55°
8
72°
53°
9
72°
56°
10
67°
53°
11
64°
50°
12
70°
51°
13
67°
50°
14
69°
49°
15
71°
51°
16
76°
50°
17
77°
52°
18
70°
51°
19
70°
52°
20
67°
53°
21
66°
52°
22
78°
58°
23
62°
51°
24
63°
53°
25
61°
52°
26
62°
51°
27
61°
49°
28
60°
49°
29
60°
48°
30
61°
49°
1
60°
51°
2
61°
51°
3
60°
47°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Marietta-Alderwood
Marietta-Alderwood's September 2026 forecast shows daily high temperatures ranging from 60° to 78°, with overnight lows between 47° and 58°. The average high for September is 66° with an average low of 51°. 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 Marietta-Alderwood. See also: October | November | December.
