S
M
T
W
T
F
S
30
90°
74°
31
93°
73°
1
94°
73°
2
96°
75°
3
95°
73°
4
93°
76°
5
91°
75°
6
96°
72°
7
90°
69°
8
91°
70°
9
90°
72°
10
94°
73°
11
92°
73°
12
90°
73°
13
93°
73°
14
97°
72°
15
94°
73°
16
89°
70°
17
91°
66°
18
93°
66°
19
94°
72°
20
90°
71°
21
92°
68°
22
91°
71°
23
86°
67°
24
79°
60°
25
80°
61°
26
83°
53°
27
83°
54°
28
80°
58°
29
81°
61°
30
81°
62°
1
79°
62°
2
82°
58°
3
85°
63°
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 79° to 92°, with overnight lows between 53° and 71°. The average high for September is 83° with an average low of 61°. 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.
