S
M
T
W
T
F
S
30
81°
56°
31
77°
49°
1
80°
47°
2
78°
47°
3
65°
59°
4
80°
60°
5
72°
53°
6
69°
50°
7
76°
57°
8
71°
48°
9
63°
59°
10
76°
58°
11
67°
50°
12
70°
52°
13
70°
55°
14
74°
53°
15
68°
54°
16
68°
48°
17
67°
49°
18
66°
48°
19
65°
50°
20
64°
47°
21
61°
50°
22
61°
51°
23
64°
51°
24
67°
50°
25
63°
50°
26
63°
47°
27
60°
45°
28
61°
45°
29
66°
49°
30
67°
49°
1
67°
48°
2
64°
49°
3
63°
48°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Castine
Castine's September 2026 forecast shows daily high temperatures ranging from 60° to 76°, with overnight lows between 45° and 59°. The average high for September is 66° with an average low of 50°. 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 Castine. See also: October | November | December.
