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
65°
47°
25
67°
58°
26
66°
58°
27
65°
56°
28
72°
54°
29
74°
64°
30
70°
64°
1
66°
44°
2
64°
44°
3
66°
49°
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 64° to 74°, with overnight lows between 44° and 64°. The average high for September is 69° 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.
