Click on a day for an hourly weather forecast
The temperatures in Allentown in September are comfortable with low of 15°C and and high up to 24°C.
You can expect about 3 to 8 days of rain in Allentown during the month of September. It’s a good idea to bring along your umbrella so that you don’t get caught in poor weather.
Our weather forecast can give you a great sense of what weather to expect in Allentown in September 2025.
If you’re planning to visit Allentown in the near future, we highly recommend that you review the 14 day weather forecast for Allentown before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | 1° / -5° | 6 | 15 | 10 | 109 mm | Awful | Allentown in January |
| February | 3° / -4° | 7 | 11 | 11 | 124 mm | Awful | Allentown in February |
| March | 9° / 0° | 7 | 17 | 7 | 136 mm | Awful | Allentown in March |
| April | 15° / 6° | 8 | 21 | 1 | 140 mm | Ok | Allentown in April |
| May | 21° / 11° | 9 | 22 | 0 | 152 mm | Ok | Allentown in May |
| June | 26° / 16° | 8 | 22 | 0 | 146 mm | Good | Allentown in June |
| July | 29° / 19° | 8 | 23 | 0 | 153 mm | Ok | Allentown in July |
| August | 28° / 18° | 7 | 24 | 0 | 172 mm | Good | Allentown in August |
| September | 24° / 15° | 6 | 24 | 0 | 120 mm | Perfect | Allentown in September |
| October | 17° / 9° | 6 | 25 | 0 | 140 mm | Good | Allentown in October |
| November | 10° / 3° | 5 | 23 | 1 | 103 mm | Ok | Allentown in November |
| December | 5° / -1° | 7 | 17 | 7 | 135 mm | Awful | Allentown in December |