S
M
T
W
T
F
S
30
76°
57°
31
75°
58°
1
76°
62°
2
77°
63°
3
81°
63°
4
81°
64°
5
83°
62°
6
81°
61°
7
76°
61°
8
75°
58°
9
76°
61°
10
77°
61°
11
79°
60°
12
81°
60°
13
83°
61°
14
81°
60°
15
79°
59°
16
75°
59°
17
76°
58°
18
79°
58°
19
78°
59°
20
79°
59°
21
80°
55°
22
81°
55°
23
81°
44°
24
77°
46°
25
74°
44°
26
72°
52°
27
74°
55°
28
78°
57°
29
81°
52°
30
76°
42°
1
75°
39°
2
67°
48°
3
68°
45°
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 67° to 83°, with overnight lows between 39° and 64°. The average high for September is 77° with an average low of 56°. 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.
