September weather forecastWilliamstown, PA
September
Weather in September
September, the first month of the autumn in Williamstown, is still a pleasant month, with an average temperature fluctuating between 73.2°F (22.9°C) and 54.1°F (12.3°C).Temperature
September ushers in a minute temperature change, with average high-temperatures reducing from August's moderately hot 80.2°F (26.8°C) to an agreeable 73.2°F (22.9°C). Williamstown encounters an average low-temperature of 54.1°F (12.3°C) during September nights.Humidity
In September, the average relative humidity is 80%.Rainfall
In Williamstown, in September, during 11.5 rainfall days, 1.81" (46mm) of precipitation is typically accumulated. Throughout the year, there are 148.4 rainfall days, and 25.55" (649mm) of precipitation is accumulated.Snowfall
In Williamstown, snow does not fall in June through September.Daylight
The average length of the day in September is 12h and 27min.On the first day of September, sunrise is at 6:34 am and sunset at 7:38 pm. On the last day of the month, sunrise is at 7:02 am and sunset at 6:49 pm EDT.
Sunshine
The average sunshine in September is 8.7h.UV index
In Williamstown, the average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a medium health hazard from unprotected exposure to Sun's UV rays for the ordinary person.Note: The maximum daily UV index of 4 in September interprets into the following recommendations:
Safety measures are advised. Light-skinned individuals may experience burns in under half an hour. Considering the harmful UV rays from the Sun during midday, it's essential to reduce exposure. Using UVA and UVB-protective sunglasses and sun-protective clothing is effective against UV radiation.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Williamstown, PA
- Average high temperature in September: 73.2°F
The warmest month (with the highest average high temperature) is July (82.2°F).
The month with the lowest average high temperature is January (33.4°F).
- Average low temperature in September: 54.1°F
The month with the highest average low temperature is July (62.1°F).
The coldest month (with the lowest average low temperature) is January (20.8°F).
Average pressure in September
Williamstown, PA
- Average pressure in September: 30.06"Hg
The month with the highest atmospheric pressure is November (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.94"Hg).
Average wind speed in September
Williamstown, PA
- Average wind speed in September: 5.3mph
The windiest months (with the highest average wind speed) are March and April (8.3mph).
The calmest month (with the lowest average wind speed) is August (4.6mph).
Average humidity in September
Williamstown, PA
- Average humidity in September: 80%
The month with the highest relative humidity is February (82%).
The month with the lowest relative humidity is April (76%).
Average rainfall in September
Williamstown, PA
- Average rainfall in September: 1.81"
The wettest month (with the highest rainfall) is May (2.95").
The driest month (with the least rainfall) is February (1.54").
Average rainfall days in September
Williamstown, PA
- Average rainfall days in September: 11.5 days
The month with the highest number of rainy days is May (17.4 days).
The month with the least rainy days is January (7.2 days).
Average snowfall in September
Williamstown, PA
- Average snowfall in September: 0"
The month with the highest snowfall is March (3.43").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Williamstown, PA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (6.9 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Williamstown, 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 18min).
The month with the least sunshine is February (Average sunshine: 4h and 12min).
Average sunshine days in September
Williamstown, PA
- Average sunshine days in September: 15.5 days
The month with the most sunshine days is November (18.8 days).
The month with the least sunshine days is May (10.8 days).
Average UV index in September
Williamstown, 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
Williamstown, PA
- Average cloud cover in September: 39
The months with the most cloud cover are February and December (Cloud cover 54).
The month with the least cloud cover is July (Cloud cover 33).
Average visibility in September
Williamstown, PA
- Average visibility in September: 5mi
The months with the highest visibility are January, March, April, June, July, November and December (6mi).
The months with the lowest visibility are February, May, August, September and October (5mi).
