S
M
T
W
T
F
S
30
80°
63°
31
79°
65°
1
81°
65°
2
79°
58°
3
79°
55°
4
76°
55°
5
76°
56°
6
78°
56°
7
80°
57°
8
82°
63°
9
82°
63°
10
80°
55°
11
77°
56°
12
77°
61°
13
78°
53°
14
76°
53°
15
73°
51°
16
75°
52°
17
74°
55°
18
77°
56°
19
78°
59°
20
78°
58°
21
81°
58°
22
78°
59°
23
80°
58°
24
74°
58°
25
76°
57°
26
79°
57°
27
79°
56°
28
78°
56°
29
80°
55°
30
79°
56°
1
79°
56°
2
78°
48°
3
78°
45°
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 82°, with overnight lows between 45° and 65°. The average high for September is 78° with an average low of 57°. 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.
