S
M
T
W
T
F
S
30
98°
73°
31
98°
73°
1
98°
75°
2
99°
77°
3
87°
75°
4
88°
73°
5
92°
73°
6
93°
73°
7
96°
74°
8
94°
73°
9
95°
72°
10
96°
73°
11
96°
72°
12
95°
73°
13
95°
73°
14
92°
71°
15
90°
67°
16
93°
70°
17
93°
70°
18
89°
69°
19
92°
69°
20
92°
70°
21
92°
70°
22
92°
69°
23
91°
69°
24
91°
68°
25
89°
68°
26
90°
67°
27
85°
63°
28
83°
59°
29
84°
59°
30
83°
58°
1
87°
59°
2
89°
65°
3
84°
57°
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 83° to 99°, with overnight lows between 57° and 77°. The average high for September is 91° with an average low of 69°. 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.
