S
M
T
W
T
F
S
30
88°
74°
31
91°
75°
1
93°
75°
2
92°
75°
3
93°
74°
4
86°
74°
5
89°
74°
6
92°
74°
7
93°
76°
8
92°
74°
9
93°
73°
10
89°
75°
11
89°
74°
12
89°
73°
13
93°
73°
14
94°
74°
15
95°
74°
16
92°
75°
17
90°
69°
18
91°
67°
19
95°
69°
20
94°
72°
21
93°
69°
22
92°
70°
23
92°
71°
24
89°
70°
25
83°
64°
26
85°
64°
27
89°
61°
28
89°
61°
29
89°
64°
30
88°
70°
1
86°
71°
2
84°
70°
3
83°
72°
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 89°, with overnight lows between 61° and 72°. The average high for September is 87° with an average low of 67°. 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.
