September weather forecastAllentown, PA
September
Weather in September
September sees Allentown in transition from summer to fall, with temperatures starting to cool down steadily. Outdoor enthusiasts continue to enjoy activities in the lower temperatures and longer sunshine hours compared to August. The month receives less rainfall, enabling residents and visitors to use this window for several end-of-summer fetes. The tail end of the month brings forth the vibrant hues of fall, adding seasonal charm to the cityscape.Temperature
The arrival of September suggests a slight decrease in the average high-temperature, moving from a warm 81°F (27.2°C) in August to a still moderately hot 74.3°F (23.5°C). Throughout the nights in September, Allentown experiences an average low-temperature of 55°F (12.8°C).Humidity
In September, the average relative humidity is 79%.Rainfall
The month with the least rainfall is September, when the rain falls for 11.5 days and typically collects 1.61" (41mm) of precipitation.Snowfall
In Allentown, snow does not fall in June through September.Daylight
In September, the average length of the day is 12h and 27min.On the first day of the month, sunrise is at 6:29 am and sunset at 7:33 pm. On the last day of September, sunrise is at 6:58 am and sunset at 6:45 pm EDT.
Sunshine
The average sunshine in September is 8.7h.UV index
The average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a moderate threat to health from exposure to the Sun's UV radiation for ordinary individuals.Note: In September, the average maximum UV index of 4 translates into the following recommendations:
Act with care - The need to guard against sun damage is communicated. Exposing oneself to the midday Sun can be harmful due to the strong UV radiation; limit your time outside. A wide-brimmed hat provides unparalleled sun protection for sensitive areas like the eyes, ears, and neck.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Allentown, PA
- Average high temperature in September: 74.3°F
The warmest month (with the highest average high temperature) is July (83.8°F).
The month with the lowest average high temperature is January (34°F).
- Average low temperature in September: 55°F
The month with the highest average low temperature is July (63.5°F).
The coldest month (with the lowest average low temperature) is January (21.6°F).
Average pressure in September
Allentown, PA
- Average pressure in September: 30.06"Hg
The month with the highest atmospheric pressure is November (30.12"Hg).
The month with the lowest atmospheric pressure is June (29.94"Hg).
Average wind speed in September
Allentown, PA
- Average wind speed in September: 5.5mph
The windiest month (with the highest average wind speed) is March (8.1mph).
The calmest month (with the lowest average wind speed) is August (5mph).
Average humidity in September
Allentown, PA
- Average humidity in September: 79%
The month with the highest relative humidity is February (82%).
The months with the lowest relative humidity are April and July (76%).
Average rainfall in September
Allentown, PA
- Average rainfall in September: 1.61"
The wettest month (with the highest rainfall) is July (3.03").
The driest month (with the least rainfall) is September (1.61").
Average rainfall days in September
Allentown, PA
- Average rainfall days in September: 11.5 days
The month with the highest number of rainy days is May (16.9 days).
The month with the least rainy days is January (6.7 days).
Average snowfall in September
Allentown, PA
- Average snowfall in September: 0"
The month with the highest snowfall is March (4.37").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Allentown, PA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (6.6 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Allentown, PA
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 18min).
- Average sunshine in September: 8h and 42min
The month with the most sunshine is July (Average sunshine: 10h and 24min).
The month with the least sunshine is February (Average sunshine: 4h and 24min).
Average sunshine days in September
Allentown, PA
- Average sunshine days in September: 16.5 days
The month with the most sunshine days is January (20.5 days).
The month with the least sunshine days is May (11.8 days).
Average UV index in September
Allentown, PA
- Average UV index in September: 4
The months with the highest UV index are June and July (UV index 6).
The months with the lowest UV index are January, February, March, November and December (UV index 2).
Average cloud cover in September
Allentown, PA
- Average cloud cover in September: 39
The month with the most cloud cover is February (Cloud cover 52).
The month with the least cloud cover is July (Cloud cover 34).
Average visibility in September
Allentown, PA
- Average visibility in September: 5mi
The months with the highest visibility are April, July and November (6mi).
The months with the lowest visibility are January, February, March, May, June, August, September, October and December (5mi).
