S
M
T
W
T
F
S
30
98°
78°
31
89°
68°
1
94°
67°
2
95°
70°
3
95°
68°
4
96°
69°
5
97°
70°
6
82°
68°
7
90°
62°
8
96°
65°
9
102°
68°
10
104°
85°
11
103°
78°
12
100°
83°
13
98°
79°
14
97°
78°
15
96°
70°
16
96°
75°
17
92°
71°
18
93°
73°
19
92°
66°
20
92°
62°
21
83°
67°
22
87°
59°
23
91°
60°
24
91°
64°
25
92°
68°
26
92°
66°
27
90°
67°
28
83°
61°
29
78°
65°
30
92°
63°
1
92°
66°
2
96°
68°
3
98°
67°
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 78° to 98°, with overnight lows between 63° and 68°. The average high for September is 91° with an average low of 66°. 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.
