S
M
T
W
T
F
S
30
87°
70°
31
86°
69°
1
94°
74°
2
92°
73°
3
92°
70°
4
91°
70°
5
81°
68°
6
83°
61°
7
81°
59°
8
86°
57°
9
89°
66°
10
88°
71°
11
79°
66°
12
80°
66°
13
90°
72°
14
79°
59°
15
77°
52°
16
85°
58°
17
87°
66°
18
86°
72°
19
79°
65°
20
82°
69°
21
73°
64°
22
64°
58°
23
63°
54°
24
66°
50°
25
74°
54°
26
70°
57°
27
67°
60°
28
71°
61°
29
74°
60°
30
81°
56°
1
86°
61°
2
88°
59°
3
69°
60°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Herndon
Herndon's September 2026 forecast shows daily high temperatures ranging from 69° to 88°, with overnight lows between 59° and 60°. The average high for September is 79° 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 Herndon. See also: October | November | December.
