S
M
T
W
T
F
S
30
89°
72°
31
87°
73°
1
98°
77°
2
91°
74°
3
91°
71°
4
90°
72°
5
85°
72°
6
85°
66°
7
84°
64°
8
86°
64°
9
89°
70°
10
91°
74°
11
82°
70°
12
81°
71°
13
89°
74°
14
81°
65°
15
78°
58°
16
86°
67°
17
90°
72°
18
85°
66°
19
80°
67°
20
82°
68°
21
77°
67°
22
77°
65°
23
78°
64°
24
79°
61°
25
77°
57°
26
78°
60°
27
79°
59°
28
79°
60°
29
80°
56°
30
76°
59°
1
73°
60°
2
78°
61°
3
72°
60°
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 56° and 72°. The average high for September is 79° with an average low of 63°. 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.
