S
M
T
W
T
F
S
30
80°
52°
31
76°
66°
1
77°
66°
2
73°
65°
3
83°
70°
4
84°
62°
5
79°
60°
6
74°
55°
7
79°
58°
8
82°
62°
9
80°
72°
10
85°
67°
11
78°
61°
12
76°
60°
13
77°
66°
14
78°
64°
15
77°
62°
16
78°
62°
17
77°
58°
18
70°
55°
19
77°
61°
20
77°
60°
21
73°
58°
22
72°
59°
23
72°
62°
24
75°
59°
25
72°
58°
26
74°
61°
27
75°
60°
28
74°
56°
29
66°
53°
30
67°
55°
1
66°
51°
2
65°
55°
3
66°
57°
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 65° to 85°, with overnight lows between 51° and 72°. The average high for September is 75° with an average low of 60°. 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.
