S
M
T
W
T
F
S
30
79°
62°
31
77°
68°
1
78°
64°
2
75°
68°
3
81°
68°
4
84°
64°
5
79°
63°
6
76°
62°
7
76°
62°
8
75°
61°
9
76°
62°
10
78°
62°
11
76°
64°
12
78°
64°
13
76°
62°
14
75°
60°
15
71°
59°
16
71°
63°
17
74°
58°
18
70°
55°
19
69°
55°
20
70°
59°
21
74°
62°
22
77°
63°
23
78°
62°
24
77°
60°
25
75°
60°
26
75°
59°
27
76°
60°
28
75°
60°
29
76°
57°
30
68°
53°
1
65°
52°
2
67°
57°
3
72°
58°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Ronkonkoma
Ronkonkoma's September 2026 forecast shows daily high temperatures ranging from 65° to 84°, with overnight lows between 52° and 68°. 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 Ronkonkoma. See also: October | November | December.
