S
M
T
W
T
F
S
30
76°
58°
31
77°
57°
1
74°
58°
2
76°
61°
3
75°
58°
4
76°
57°
5
76°
55°
6
75°
57°
7
73°
53°
8
74°
54°
9
74°
61°
10
73°
55°
11
73°
53°
12
74°
54°
13
73°
56°
14
76°
57°
15
77°
59°
16
78°
59°
17
79°
58°
18
78°
58°
19
77°
57°
20
76°
50°
21
69°
54°
22
69°
56°
23
73°
56°
24
74°
57°
25
75°
53°
26
74°
48°
27
69°
48°
28
66°
49°
29
65°
49°
30
65°
47°
1
66°
48°
2
64°
45°
3
Hist. Avg.
68°
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 64° to 79°, with overnight lows between 45° and 61°. The average high for September is 73° 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.
