S
M
T
W
T
F
S
30
96°
62°
31
97°
70°
1
100°
69°
2
100°
69°
3
102°
70°
4
102°
71°
5
103°
71°
6
92°
74°
7
88°
62°
8
93°
72°
9
98°
72°
10
81°
61°
11
85°
63°
12
89°
66°
13
93°
67°
14
90°
66°
15
84°
62°
16
82°
59°
17
85°
62°
18
85°
61°
19
81°
60°
20
80°
56°
21
84°
61°
22
79°
61°
23
81°
60°
24
84°
61°
25
84°
62°
26
83°
61°
27
84°
61°
28
83°
60°
29
83°
61°
30
82°
61°
1
81°
56°
2
79°
50°
3
69°
46°
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 69° to 98°, with overnight lows between 46° and 72°. The average high for September is 84° 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.
