S
M
T
W
T
F
S
30
95°
59°
31
99°
63°
1
101°
67°
2
102°
69°
3
102°
69°
4
102°
70°
5
101°
71°
6
90°
60°
7
90°
60°
8
98°
72°
9
99°
72°
10
86°
63°
11
83°
61°
12
89°
64°
13
94°
63°
14
90°
60°
15
90°
63°
16
89°
61°
17
89°
60°
18
82°
51°
19
74°
62°
20
78°
61°
21
82°
61°
22
77°
60°
23
79°
60°
24
81°
59°
25
81°
61°
26
82°
60°
27
81°
60°
28
80°
59°
29
81°
60°
30
80°
60°
1
77°
55°
2
69°
48°
3
66°
46°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Mount Vernon
Mount Vernon's September 2026 forecast shows daily high temperatures ranging from 66° to 101°, with overnight lows between 46° and 72°. The average high for September is 84° 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 Mount Vernon. See also: October | November | December.
