S
M
T
W
T
F
S
30
89°
70°
31
90°
71°
1
90°
71°
2
88°
70°
3
82°
67°
4
81°
64°
5
80°
62°
6
80°
62°
7
82°
66°
8
88°
68°
9
84°
64°
10
82°
68°
11
81°
57°
12
78°
59°
13
78°
58°
14
79°
57°
15
78°
60°
16
79°
62°
17
78°
64°
18
81°
57°
19
84°
55°
20
76°
54°
21
75°
54°
22
75°
55°
23
76°
55°
24
79°
54°
25
79°
61°
26
78°
61°
27
76°
60°
28
75°
57°
29
77°
53°
30
78°
52°
1
72°
52°
2
77°
59°
3
73°
49°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Washington
Washington's September 2026 forecast shows daily high temperatures ranging from 72° to 90°, with overnight lows between 49° and 71°. The average high for September is 80° with an average low of 60°. 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 Washington. See also: October | November | December.
