S
M
T
W
T
F
S
30
89°
76°
31
88°
72°
1
93°
74°
2
96°
72°
3
94°
75°
4
94°
76°
5
92°
75°
6
89°
73°
7
90°
75°
8
94°
70°
9
84°
57°
10
82°
65°
11
85°
63°
12
85°
62°
13
74°
58°
14
74°
54°
15
73°
56°
16
74°
58°
17
80°
57°
18
76°
58°
19
71°
55°
20
76°
53°
21
82°
60°
22
81°
59°
23
81°
60°
24
78°
60°
25
72°
59°
26
73°
59°
27
78°
58°
28
77°
59°
29
73°
57°
30
76°
51°
1
65°
47°
2
64°
44°
3
63°
42°
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 63° to 94°, with overnight lows between 42° and 75°. The average high for September is 77° 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.
