S
M
T
W
T
F
S
30
87°
57°
31
79°
55°
1
78°
57°
2
79°
61°
3
78°
56°
4
80°
63°
5
85°
62°
6
86°
55°
7
82°
56°
8
77°
54°
9
77°
53°
10
76°
60°
11
80°
53°
12
78°
54°
13
74°
52°
14
75°
59°
15
79°
60°
16
82°
51°
17
82°
49°
18
72°
49°
19
71°
51°
20
72°
52°
21
71°
52°
22
70°
50°
23
69°
54°
24
71°
54°
25
71°
55°
26
76°
56°
27
76°
49°
28
77°
47°
29
69°
49°
30
69°
54°
1
68°
55°
2
72°
52°
3
74°
46°
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 87°, with overnight lows between 46° and 63°. The average high for September is 76° with an average low of 54°. 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.
