S
M
T
W
T
F
S
30
87°
57°
31
81°
68°
1
86°
70°
2
78°
69°
3
88°
69°
4
87°
63°
5
82°
58°
6
77°
58°
7
79°
59°
8
78°
56°
9
76°
57°
10
81°
59°
11
79°
59°
12
81°
55°
13
79°
56°
14
80°
55°
15
75°
57°
16
75°
58°
17
76°
51°
18
73°
50°
19
72°
49°
20
73°
52°
21
77°
57°
22
80°
57°
23
80°
56°
24
79°
55°
25
78°
52°
26
77°
54°
27
78°
55°
28
78°
55°
29
79°
54°
30
72°
49°
1
68°
47°
2
71°
50°
3
75°
53°
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 88°, with overnight lows between 47° and 70°. The average high for September is 78° with an average low of 56°. 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.
