S
M
T
W
T
F
S
30
90°
71°
31
89°
71°
1
87°
70°
2
87°
71°
3
86°
71°
4
86°
68°
5
88°
68°
6
89°
69°
7
90°
70°
8
89°
69°
9
89°
70°
10
88°
70°
11
89°
69°
12
89°
69°
13
88°
70°
14
88°
70°
15
87°
69°
16
86°
69°
17
85°
68°
18
84°
66°
19
84°
69°
20
85°
69°
21
83°
65°
22
84°
68°
23
84°
68°
24
85°
65°
25
86°
64°
26
85°
67°
27
85°
68°
28
86°
67°
29
82°
66°
30
86°
66°
1
Hist. Avg.
84°
64°
2
Hist. Avg.
84°
64°
3
Hist. Avg.
84°
64°
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 82° to 90°, with overnight lows between 64° and 71°. The average high for September is 87° with an average low of 68°. 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.
