S
M
T
W
T
F
S
30
73°
64°
31
69°
62°
1
83°
67°
2
84°
67°
3
83°
67°
4
78°
64°
5
74°
60°
6
71°
51°
7
75°
54°
8
78°
63°
9
83°
67°
10
76°
55°
11
72°
53°
12
77°
60°
13
79°
59°
14
71°
59°
15
72°
58°
16
71°
54°
17
72°
53°
18
71°
57°
19
69°
54°
20
66°
50°
21
68°
56°
22
66°
55°
23
67°
55°
24
69°
54°
25
73°
55°
26
73°
52°
27
65°
49°
28
72°
54°
29
73°
55°
30
73°
55°
1
72°
54°
2
71°
52°
3
70°
50°
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 65° to 83°, with overnight lows between 49° and 67°. The average high for September is 72° with an average low of 55°. 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.
