S
M
T
W
T
F
S
30
80°
55°
31
79°
58°
1
80°
59°
2
81°
61°
3
81°
54°
4
78°
50°
5
77°
57°
6
80°
52°
7
77°
58°
8
79°
60°
9
80°
59°
10
81°
59°
11
81°
58°
12
78°
58°
13
80°
55°
14
78°
54°
15
72°
49°
16
74°
51°
17
73°
48°
18
72°
51°
19
74°
50°
20
70°
51°
21
70°
46°
22
73°
43°
23
67°
48°
24
66°
51°
25
64°
52°
26
72°
53°
27
71°
52°
28
71°
49°
29
73°
42°
30
73°
39°
1
63°
37°
2
59°
37°
3
58°
38°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Watertown
Watertown's September 2026 forecast shows daily high temperatures ranging from 58° to 81°, with overnight lows between 37° and 61°. The average high for September is 74° with an average low of 51°. 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 Watertown. See also: October | November | December.
