S
M
T
W
T
F
S
30
75°
63°
31
78°
67°
1
80°
68°
2
80°
67°
3
76°
65°
4
75°
61°
5
74°
60°
6
73°
59°
7
75°
65°
8
79°
60°
9
72°
58°
10
73°
58°
11
76°
54°
12
70°
56°
13
71°
56°
14
69°
55°
15
71°
56°
16
72°
55°
17
70°
54°
18
75°
56°
19
70°
53°
20
70°
52°
21
68°
52°
22
68°
54°
23
71°
56°
24
75°
53°
25
75°
57°
26
74°
58°
27
68°
54°
28
67°
54°
29
73°
53°
30
71°
49°
1
66°
53°
2
70°
58°
3
72°
47°
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 47° and 68°. The average high for September is 73° with an average low of 57°. 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.
