S
M
T
W
T
F
S
30
80°
66°
31
90°
71°
1
92°
68°
2
87°
70°
3
89°
72°
4
91°
71°
5
86°
68°
6
76°
66°
7
81°
66°
8
79°
65°
9
85°
62°
10
81°
54°
11
82°
55°
12
78°
55°
13
67°
49°
14
69°
51°
15
71°
55°
16
73°
53°
17
73°
64°
18
77°
63°
19
76°
61°
20
67°
59°
21
59°
54°
22
62°
50°
23
70°
45°
24
67°
59°
25
67°
56°
26
62°
58°
27
66°
54°
28
71°
57°
29
67°
54°
30
68°
48°
1
67°
51°
2
67°
49°
3
66°
47°
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 62° to 71°, with overnight lows between 47° and 59°. The average high for September is 67° with an average low of 53°. 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.
