S
M
T
W
T
F
S
30
77°
59°
31
78°
59°
1
76°
60°
2
76°
61°
3
77°
62°
4
75°
61°
5
77°
61°
6
76°
60°
7
75°
59°
8
74°
58°
9
73°
58°
10
75°
64°
11
74°
58°
12
74°
57°
13
77°
56°
14
77°
63°
15
75°
62°
16
75°
59°
17
72°
56°
18
72°
55°
19
73°
57°
20
77°
61°
21
73°
58°
22
71°
58°
23
76°
59°
24
74°
60°
25
76°
59°
26
69°
52°
27
72°
53°
28
67°
52°
29
66°
51°
30
68°
52°
1
67°
51°
2
Hist. Avg.
67°
46°
3
Hist. Avg.
67°
45°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Riverhead
Riverhead's September 2026 forecast shows daily high temperatures ranging from 66° to 78°, with overnight lows between 51° and 64°. The average high for September is 74° with an average low of 58°. 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 Riverhead. See also: October | November | December.
