S
M
T
W
T
F
S
30
80°
61°
31
82°
61°
1
84°
60°
2
80°
56°
3
77°
56°
4
79°
58°
5
83°
57°
6
84°
60°
7
85°
61°
8
85°
61°
9
84°
60°
10
84°
59°
11
83°
60°
12
85°
61°
13
85°
61°
14
80°
49°
15
72°
52°
16
74°
55°
17
76°
54°
18
72°
49°
19
71°
46°
20
73°
47°
21
77°
50°
22
80°
54°
23
80°
46°
24
71°
46°
25
71°
52°
26
77°
53°
27
76°
53°
28
78°
45°
29
69°
43°
30
68°
43°
1
68°
46°
2
76°
47°
3
76°
50°
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 68° to 85°, with overnight lows between 43° and 61°. The average high for September is 78° with an average low of 53°. 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.
