S
M
T
W
T
F
S
30
66°
55°
31
N/A
1
61°
52°
2
61°
56°
3
64°
53°
4
62°
50°
5
62°
50°
6
64°
53°
7
63°
51°
8
61°
52°
9
61°
51°
10
60°
49°
11
60°
51°
12
61°
50°
13
62°
48°
14
62°
51°
15
61°
50°
16
61°
51°
17
62°
51°
18
62°
50°
19
60°
48°
20
59°
50°
21
61°
51°
22
62°
49°
23
59°
48°
24
57°
49°
25
60°
50°
26
60°
50°
27
61°
49°
28
61°
49°
29
60°
48°
30
61°
49°
1
61°
49°
2
60°
48°
3
60°
49°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Dumbarton
Dumbarton's September 2026 forecast shows daily high temperatures ranging from 57° to 64°, with overnight lows between 48° and 56°. The average high for September is 61° 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 Dumbarton. See also: October | November | December.
