S
M
T
W
T
F
S
30
84°
64°
31
86°
65°
1
88°
65°
2
88°
64°
3
87°
64°
4
88°
59°
5
82°
63°
6
86°
65°
7
87°
64°
8
84°
62°
9
80°
63°
10
84°
64°
11
87°
63°
12
86°
63°
13
86°
62°
14
85°
62°
15
86°
61°
16
85°
61°
17
84°
54°
18
78°
54°
19
78°
52°
20
77°
52°
21
75°
51°
22
75°
53°
23
76°
54°
24
82°
55°
25
82°
58°
26
81°
58°
27
82°
56°
28
81°
55°
29
80°
54°
30
80°
54°
1
77°
52°
2
79°
55°
3
80°
55°
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 75° to 88°, with overnight lows between 51° and 65°. The average high for September is 82° with an average low of 59°. 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.
