S
M
T
W
T
F
S
30
88°
60°
31
82°
58°
1
80°
64°
2
80°
63°
3
84°
59°
4
85°
65°
5
86°
65°
6
87°
58°
7
84°
58°
8
78°
57°
9
78°
57°
10
80°
60°
11
83°
57°
12
81°
57°
13
76°
55°
14
75°
62°
15
80°
61°
16
83°
54°
17
82°
53°
18
74°
52°
19
73°
53°
20
73°
58°
21
72°
58°
22
73°
52°
23
72°
55°
24
72°
54°
25
73°
57°
26
75°
58°
27
78°
51°
28
78°
49°
29
70°
55°
30
71°
55°
1
70°
56°
2
73°
54°
3
74°
48°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Herndon Junction
Herndon Junction's September 2026 forecast shows daily high temperatures ranging from 70° to 88°, with overnight lows between 48° and 65°. The average high for September is 78° with an average low of 57°. 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 Junction. See also: October | November | December.
