S
M
T
W
T
F
S
30
81°
56°
31
75°
68°
1
88°
68°
2
72°
68°
3
86°
66°
4
84°
70°
5
79°
63°
6
79°
59°
7
77°
54°
8
81°
54°
9
84°
61°
10
86°
68°
11
81°
59°
12
79°
54°
13
81°
65°
14
74°
47°
15
74°
52°
16
79°
62°
17
83°
64°
18
84°
60°
19
75°
62°
20
72°
56°
21
73°
53°
22
68°
55°
23
71°
53°
24
71°
53°
25
73°
54°
26
74°
50°
27
74°
56°
28
76°
55°
29
76°
52°
30
70°
49°
1
69°
52°
2
70°
54°
3
74°
50°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Allentown
Allentown's September 2026 forecast shows daily high temperatures ranging from 68° to 84°, with overnight lows between 47° and 65°. The average high for September is 74° 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 Allentown. See also: October | November | December.
