S
M
T
W
T
F
S
30
79°
60°
31
80°
63°
1
84°
61°
2
79°
55°
3
79°
54°
4
76°
55°
5
77°
56°
6
79°
56°
7
82°
59°
8
83°
63°
9
84°
58°
10
81°
54°
11
77°
61°
12
80°
59°
13
81°
52°
14
76°
52°
15
74°
51°
16
75°
52°
17
76°
58°
18
80°
51°
19
78°
58°
20
79°
57°
21
82°
58°
22
79°
58°
23
81°
57°
24
74°
58°
25
79°
57°
26
80°
57°
27
81°
56°
28
81°
55°
29
80°
56°
30
80°
56°
1
79°
54°
2
80°
46°
3
79°
45°
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 74° to 84°, with overnight lows between 45° and 63°. The average high for September is 79° with an average low of 56°. 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.
