S
M
T
W
T
F
S
30
70°
48°
31
69°
48°
1
68°
50°
2
70°
49°
3
69°
51°
4
70°
49°
5
69°
47°
6
68°
48°
7
68°
46°
8
69°
45°
9
68°
53°
10
67°
46°
11
66°
45°
12
68°
45°
13
70°
52°
14
72°
46°
15
71°
51°
16
72°
51°
17
72°
50°
18
73°
51°
19
72°
49°
20
72°
45°
21
63°
49°
22
63°
46°
23
64°
49°
24
66°
48°
25
65°
43°
26
67°
39°
27
67°
41°
28
58°
40°
29
58°
41°
30
56°
38°
1
Hist. Avg.
62°
44°
2
Hist. Avg.
62°
43°
3
Hist. Avg.
61°
43°
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 56° to 73°, with overnight lows between 38° and 53°. The average high for September is 68° with an average low of 47°. 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.
