S
M
T
W
T
F
S
30
90°
57°
31
94°
58°
1
93°
59°
2
90°
56°
3
89°
56°
4
88°
57°
5
89°
57°
6
90°
56°
7
89°
55°
8
89°
57°
9
88°
58°
10
88°
61°
11
89°
58°
12
89°
60°
13
91°
63°
14
94°
62°
15
94°
61°
16
95°
60°
17
94°
58°
18
93°
57°
19
92°
58°
20
90°
59°
21
92°
60°
22
93°
60°
23
92°
59°
24
87°
59°
25
82°
58°
26
81°
56°
27
82°
57°
28
83°
58°
29
84°
59°
30
83°
59°
1
82°
57°
2
81°
54°
3
81°
56°
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 81° to 95°, with overnight lows between 54° and 63°. The average high for September is 89° with an average low of 58°. 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.
