S
M
T
W
T
F
S
30
95°
64°
31
98°
69°
1
98°
73°
2
97°
73°
3
97°
73°
4
99°
73°
5
100°
74°
6
103°
74°
7
99°
71°
8
101°
71°
9
97°
72°
10
98°
71°
11
97°
70°
12
96°
70°
13
92°
65°
14
90°
66°
15
89°
64°
16
85°
59°
17
88°
63°
18
84°
63°
19
86°
63°
20
88°
62°
21
88°
64°
22
87°
63°
23
88°
62°
24
87°
62°
25
86°
61°
26
81°
58°
27
76°
52°
28
76°
50°
29
74°
48°
30
75°
52°
1
79°
53°
2
82°
54°
3
73°
52°
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 73° to 103°, with overnight lows between 48° and 74°. The average high for September is 88° with an average low of 63°. 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.
