S
M
T
W
T
F
S
30
68°
63°
31
75°
64°
1
86°
67°
2
84°
65°
3
81°
62°
4
72°
58°
5
76°
56°
6
75°
54°
7
76°
50°
8
76°
63°
9
76°
59°
10
73°
44°
11
72°
49°
12
77°
59°
13
75°
53°
14
68°
57°
15
73°
54°
16
67°
49°
17
66°
52°
18
61°
46°
19
61°
47°
20
64°
47°
21
61°
46°
22
61°
50°
23
63°
51°
24
66°
51°
25
69°
50°
26
69°
49°
27
62°
49°
28
68°
50°
29
69°
51°
30
69°
51°
1
68°
50°
2
66°
47°
3
65°
42°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Waterloo
Waterloo's September 2026 forecast shows daily high temperatures ranging from 61° to 77°, with overnight lows between 42° and 63°. The average high for September is 68° 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 Waterloo. See also: October | November | December.
