S
M
T
W
T
F
S
30
82°
66°
31
87°
66°
1
90°
71°
2
94°
71°
3
91°
67°
4
85°
67°
5
82°
61°
6
79°
57°
7
77°
57°
8
78°
58°
9
81°
61°
10
76°
58°
11
75°
53°
12
76°
54°
13
74°
54°
14
75°
52°
15
77°
57°
16
77°
57°
17
76°
56°
18
76°
56°
19
77°
57°
20
78°
57°
21
78°
56°
22
77°
56°
23
77°
55°
24
76°
56°
25
77°
55°
26
77°
53°
27
76°
54°
28
76°
54°
29
75°
53°
30
74°
52°
1
73°
52°
2
74°
51°
3
74°
52°
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 73° to 94°, with overnight lows between 51° and 71°. The average high for September is 78° with an average low of 57°. 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.
