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°
66°
21
70°
61°
22
65°
54°
23
61°
54°
24
63°
50°
25
70°
50°
26
71°
53°
27
72°
50°
28
69°
50°
29
70°
52°
30
72°
51°
1
74°
52°
2
71°
51°
3
69°
56°
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 61° to 82°, with overnight lows between 50° and 66°. The average high for September is 70° with an average low of 54°. 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.
