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°
60°
8
94°
60°
9
99°
73°
10
79°
71°
11
82°
69°
12
89°
66°
13
89°
67°
14
91°
68°
15
95°
69°
16
92°
71°
17
88°
65°
18
83°
58°
19
74°
53°
20
81°
57°
21
77°
56°
22
80°
57°
23
81°
54°
24
84°
61°
25
83°
60°
26
82°
59°
27
83°
59°
28
83°
58°
29
82°
60°
30
81°
58°
1
81°
56°
2
79°
57°
3
81°
57°
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 74° to 95°, 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.
