S
M
T
W
T
F
S
30
79°
62°
31
77°
68°
1
78°
66°
2
75°
65°
3
85°
70°
4
84°
70°
5
80°
66°
6
73°
60°
7
79°
56°
8
80°
61°
9
79°
62°
10
86°
70°
11
78°
62°
12
76°
57°
13
79°
68°
14
73°
59°
15
71°
58°
16
77°
67°
17
80°
68°
18
80°
59°
19
72°
63°
20
69°
64°
21
72°
62°
22
68°
55°
23
69°
56°
24
69°
57°
25
71°
57°
26
72°
58°
27
71°
56°
28
70°
54°
29
74°
56°
30
67°
53°
1
66°
53°
2
68°
57°
3
72°
54°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Smithtown
Smithtown's September 2026 forecast shows daily high temperatures ranging from 66° to 80°, with overnight lows between 53° and 68°. The average high for September is 71° with an average low of 58°. 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 Smithtown. See also: October | November | December.
