S
M
T
W
T
F
S
30
82°
70°
31
81°
70°
1
82°
66°
2
75°
62°
3
74°
64°
4
74°
62°
5
75°
62°
6
77°
68°
7
81°
69°
8
79°
68°
9
75°
68°
10
78°
67°
11
80°
68°
12
80°
68°
13
79°
69°
14
79°
59°
15
72°
58°
16
69°
59°
17
72°
58°
18
70°
56°
19
69°
57°
20
70°
59°
21
76°
60°
22
76°
63°
23
75°
55°
24
76°
54°
25
71°
54°
26
68°
55°
27
72°
60°
28
73°
60°
29
74°
52°
30
70°
52°
1
66°
57°
2
67°
57°
3
71°
56°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Port Jefferson
Port Jefferson's September 2026 forecast shows daily high temperatures ranging from 66° to 82°, with overnight lows between 52° and 70°. The average high for September is 75° with an average low of 61°. 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 Port Jefferson. See also: October | November | December.
