S
M
T
W
T
F
S
30
70°
45°
31
74°
50°
1
78°
53°
2
80°
54°
3
79°
52°
4
70°
43°
5
71°
44°
6
70°
46°
7
74°
46°
8
75°
53°
9
71°
45°
10
71°
44°
11
72°
46°
12
71°
52°
13
69°
44°
14
68°
42°
15
68°
43°
16
69°
44°
17
69°
45°
18
71°
44°
19
76°
48°
20
76°
43°
21
68°
45°
22
68°
44°
23
64°
43°
24
66°
42°
25
64°
39°
26
66°
40°
27
64°
42°
28
66°
48°
29
71°
47°
30
61°
41°
1
73°
50°
2
69°
48°
3
Hist. Avg.
66°
43°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Boston Harbor
Boston Harbor's September 2026 forecast shows daily high temperatures ranging from 61° to 80°, with overnight lows between 39° and 54°. The average high for September is 70° with an average low of 46°. 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 Boston Harbor. See also: October | November | December.
