S
M
T
W
T
F
S
30
82°
57°
31
76°
56°
1
74°
57°
2
74°
62°
3
75°
57°
4
77°
63°
5
77°
63°
6
80°
57°
7
78°
56°
8
72°
55°
9
73°
55°
10
72°
61°
11
74°
54°
12
77°
55°
13
71°
54°
14
70°
59°
15
73°
61°
16
76°
52°
17
78°
51°
18
69°
51°
19
67°
52°
20
68°
52°
21
68°
53°
22
66°
51°
23
66°
54°
24
67°
56°
25
68°
55°
26
72°
56°
27
72°
53°
28
73°
48°
29
66°
48°
30
64°
54°
1
65°
55°
2
69°
54°
3
70°
53°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Sag Harbor
Sag Harbor's September 2026 forecast shows daily high temperatures ranging from 64° to 82°, with overnight lows between 48° and 63°. The average high for September is 72° with an average low of 55°. 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 Sag Harbor. See also: October | November | December.
