S
M
T
W
T
F
S
30
82°
62°
31
87°
68°
1
84°
69°
2
91°
72°
3
91°
69°
4
86°
67°
5
80°
58°
6
81°
59°
7
79°
56°
8
81°
62°
9
86°
61°
10
81°
58°
11
79°
52°
12
77°
56°
13
74°
54°
14
72°
53°
15
76°
49°
16
76°
54°
17
75°
52°
18
73°
53°
19
78°
53°
20
76°
54°
21
76°
53°
22
75°
51°
23
73°
48°
24
69°
50°
25
75°
51°
26
73°
50°
27
69°
45°
28
64°
42°
29
63°
41°
30
64°
41°
1
62°
39°
2
66°
48°
3
69°
47°
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 62° to 91°, with overnight lows between 39° and 72°. The average high for September is 75° with an average low of 53°. 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.
