Allentown, PA weather in September
Expect mild weather with some rain in Allentown in September, with highs near 77°F and lows near 55°F. Rain falls on about 10 days. Good for outdoor plans.
- Normal high
- 77°F
- Normal low
- 55°F
- Wet days
- 10
- 4.8 in total
- Muggy days
- 5
- dew point 65°F+
How September changes from start to finish
| September 1 | September 30 | |
|---|---|---|
| Normal high | 82°F | 72°F |
| Normal low | 60°F | 50°F |
| Chance of a wet day | 31% | 33% |
| Sunrise / sunset | 6:29 am / 7:34 pm | 6:57 am / 6:46 pm |
| Daylight | 13.1 h | 11.8 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Eastern Time).
A typical September day
- 6 am57°Fdew point 54°F
- 9 am66°Fdew point 57°F
- Noon73°Fdew point 56°F
- 3 pm75°Fdew point 56°F
- 6 pm71°Fdew point 56°F
- 9 pm64°Fdew point 56°F
NOAA hourly normals (local standard time) from Allentown Intl Airport (4 mi away); average wind 6 mph; clear or few clouds in 54% of daytime hours, mostly cloudy or overcast in 35%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F14 of 30
- Hot dayshigh 90°F or more2 of 30
- Muggy daysdaily mean dew point 65°F or more5 of 30
- Wet daysat least 0.01 in of rain or melted snow10 of 30
- Notable rainat least 0.10 in7 of 30
- Freezing nightslow 32°F or below0 of 30
- Snow on the groundsnow depth 1 in or more0 of 30
Average days per September, counted from daily records for each year 1991-2020.
Rain in September
Normal precipitation is 4.8 in; a dry September brings about 2.7 in and a wet one about 6.4 in (25th and 75th percentiles). About 3 days bring half an inch or more, and about 2 an inch or more.
How September varies from year to year
- Warmest September, 1991-20202015: average high 82°F
- Coolest September2006: average high 72°F
- Wettest September2011: 13.0 in
- Driest September2007: 0.6 in
- Highest reading96°F (September 2, 2010)
- Lowest reading32°F (September 29, 2000)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
September compared with August and October
| August | September | October | |
|---|---|---|---|
| Normal high | 84°F | 77°F | 66°F |
| Normal low | 63°F | 55°F | 44°F |
| Wet days | 10 | 10 | 10 |
| Comfortable days | 5 | 14 | 13 |
| Daylight | 13.7 h | 12.5 h | 11.1 h |
Highs change by -7°F from August and -11°F into October.
Nearby alternatives in September
- Cooler: Worcester, MA223 mi · high 71°F · 10 wet days
How Allentown ranks in September
- Normal high236th warmest of 378 cities; 2nd of 4 in Pennsylvania
- Wet days293rd driest of 378
- Comfortable days104th most of 342
What to pack for Allentown in September
- A rain jacket or umbrella – rain on about 10 days
Heating and cooling
September has 69 heating degree days and 108 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Allentown in September?
The normal high is 77°F and the normal low is 55°F. From 1991 to 2020 the hottest September reading was 96°F (September 2, 2010).
Does it rain a lot in Allentown in September?
About 10 days in September have at least 0.01 in of precipitation, and the normal total is 4.8 in. The wettest September in 1991-2020 was in 2011 (13.0 in); the driest was in 2007 (0.6 in).
Is September a good time to visit Allentown?
September ranks 2nd of 12 months on our comfort score for Allentown (66 out of 100). It has about 14 comfortable days and about 2 days at 90°F or hotter. The best month is May.
Where the numbers come from
- Temperature, rain, snowfall, snow depth, frost dates, humidity and wind by hour and cloud cover: Allentown Intl Airport (USW00014737), 3.6 mi NE of the city center, 390 ft . NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Lehigh Valley International Airport (725170-14737), 3.6 mi NE of the city center, 385 ft . Hourly observations, 1991-2020.