S
M
T
W
T
F
S
30
72°
49°
31
73°
49°
1
71°
48°
2
70°
51°
3
71°
51°
4
69°
52°
5
70°
49°
6
71°
50°
7
68°
48°
8
69°
47°
9
67°
48°
10
69°
54°
11
68°
47°
12
69°
47°
13
72°
46°
14
71°
51°
15
71°
50°
16
68°
46°
17
66°
44°
18
68°
45°
19
69°
51°
20
70°
51°
21
72°
50°
22
68°
49°
23
71°
47°
24
69°
45°
25
67°
48°
26
63°
41°
27
69°
42°
28
61°
41°
29
61°
41°
30
63°
44°
1
62°
39°
2
Hist. Avg.
66°
45°
3
Hist. Avg.
66°
45°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Alton Bay
Alton Bay's September 2026 forecast shows daily high temperatures ranging from 61° to 73°, with overnight lows between 39° and 54°. The average high for September is 68° with an average low of 47°. 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 Alton Bay. See also: October | November | December.
