S
M
T
W
T
F
S
30
90°
73°
31
88°
72°
1
88°
73°
2
89°
72°
3
89°
72°
4
90°
71°
5
86°
71°
6
85°
72°
7
86°
72°
8
87°
71°
9
88°
72°
10
89°
72°
11
90°
71°
12
90°
72°
13
89°
71°
14
88°
71°
15
87°
70°
16
88°
70°
17
88°
69°
18
85°
70°
19
84°
70°
20
83°
68°
21
87°
65°
22
85°
64°
23
89°
65°
24
85°
64°
25
86°
67°
26
85°
64°
27
86°
66°
28
87°
66°
29
87°
65°
30
86°
65°
1
87°
64°
2
88°
63°
3
86°
64°
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 83° to 90°, with overnight lows between 63° and 73°. The average high for September is 87° with an average low of 69°. 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.
