S
M
T
W
T
F
S
30
84°
63°
31
80°
63°
1
79°
62°
2
78°
62°
3
78°
67°
4
77°
62°
5
82°
62°
6
78°
61°
7
77°
60°
8
76°
61°
9
77°
61°
10
79°
67°
11
81°
66°
12
75°
64°
13
75°
66°
14
81°
65°
15
Hist. Avg.
78°
65°
16
Hist. Avg.
77°
64°
17
Hist. Avg.
77°
64°
18
Hist. Avg.
76°
64°
19
Hist. Avg.
76°
63°
20
Hist. Avg.
76°
63°
21
Hist. Avg.
75°
63°
22
Hist. Avg.
75°
62°
23
Hist. Avg.
75°
62°
24
Hist. Avg.
74°
62°
25
Hist. Avg.
74°
61°
26
Hist. Avg.
74°
61°
27
Hist. Avg.
73°
60°
28
Hist. Avg.
73°
60°
29
Hist. Avg.
72°
60°
30
Hist. Avg.
72°
59°
1
Hist. Avg.
72°
59°
2
Hist. Avg.
71°
58°
3
Hist. Avg.
71°
58°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Mount Vernon
Mount Vernon's September 2026 forecast shows daily high temperatures ranging from 75° to 84°, with overnight lows between 60° and 67°. The average high for September is 79° with an average low of 63°. 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.
