S
M
T
W
T
F
S
30
91°
73°
31
91°
73°
1
90°
72°
2
91°
73°
3
92°
73°
4
88°
72°
5
89°
71°
6
89°
72°
7
90°
70°
8
90°
71°
9
91°
71°
10
91°
70°
11
90°
71°
12
90°
70°
13
87°
71°
14
84°
68°
15
88°
69°
16
91°
69°
17
92°
70°
18
91°
67°
19
89°
63°
20
83°
64°
21
83°
66°
22
86°
62°
23
87°
61°
24
88°
66°
25
88°
63°
26
87°
65°
27
81°
65°
28
83°
62°
29
82°
63°
30
85°
64°
1
86°
63°
2
84°
63°
3
86°
62°
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 81° to 92°, with overnight lows between 61° and 73°. The average high for September is 88° with an average low of 68°. 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.
