September weather forecastMercersburg, PA
September
Weather in September
The first month of the autumn, September, is still a warm month in Mercersburg, Pennsylvania, with an average temperature fluctuating between 55.4°F (13°C) and 75°F (23.9°C).Temperature
The average high-temperature shows a slight dip in September, from August's 82°F (27.8°C) to a still moderately hot 75°F (23.9°C). In Mercersburg, September's nights observe an average temperature dip to a moderate 55.4°F (13°C).Humidity
In Mercersburg, the average relative humidity in September is 78%.Rainfall
September is the month with the least rainfall. Rain falls for 14 days and accumulates 2.05" (52mm) of precipitation.Snowfall
In Mercersburg, snow does not fall in May through September.Daylight
In September, the average length of the day in Mercersburg is 12h and 26min.On the first day of the month, sunrise is at 6:40 am and sunset at 7:42 pm. On the last day of September, sunrise is at 7:07 am and sunset at 6:55 pm EDT.
Sunshine
In September, the average sunshine is 8.6h.UV index
In Mercersburg, Pennsylvania, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a moderate threat to health from unsafe exposure to UV radiation for ordinary individuals.Note: A daily maximum UV index of 4 in September translates into the following instructions:
Put precautions into practice - Ensuring skin and eye safety is a necessity. For skin protection, it's recommended to minimize Sun exposure during its peak hours around midday. Tightly woven clothing, when worn loosely, shields effectively against the Sun.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Mercersburg, PA
- Average high temperature in September: 75°F
The warmest month (with the highest average high temperature) is July (84.7°F).
The month with the lowest average high temperature is January (35.2°F).
- Average low temperature in September: 55.4°F
The month with the highest average low temperature is July (62.6°F).
The coldest month (with the lowest average low temperature) is January (22.1°F).
Average pressure in September
Mercersburg, PA
- Average pressure in September: 30.06"Hg
The month with the highest atmospheric pressure is November (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.95"Hg).
Average wind speed in September
Mercersburg, PA
- Average wind speed in September: 4.8mph
The windiest month (with the highest average wind speed) is January (7.5mph).
The calmest month (with the lowest average wind speed) is August (4.3mph).
Average humidity in September
Mercersburg, PA
- Average humidity in September: 78%
The months with the highest relative humidity are February, May, October and December (79%).
The months with the lowest relative humidity are April and July (75%).
Average rainfall in September
Mercersburg, PA
- Average rainfall in September: 2.05"
The wettest month (with the highest rainfall) is May (3.19").
The driest month (with the least rainfall) is September (2.05").
Average rainfall days in September
Mercersburg, PA
- Average rainfall days in September: 14 days
The month with the highest number of rainy days is May (18.8 days).
The month with the least rainy days is November (9.9 days).
Average snowfall in September
Mercersburg, PA
- Average snowfall in September: 0"
The month with the highest snowfall is January (5.2").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Mercersburg, PA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (9.9 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Mercersburg, PA
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 54min).
The month with the shortest days is December (Average daylight: 9h and 24min).
- Average sunshine in September: 8h and 36min
The month with the most sunshine is July (Average sunshine: 10h and 30min).
The month with the least sunshine is January (Average sunshine: 4h and 36min).
Average sunshine days in September
Mercersburg, PA
- Average sunshine days in September: 14.2 days
The month with the most sunshine days is November (18 days).
The month with the least sunshine days is May (10.3 days).
Average UV index in September
Mercersburg, PA
- Average UV index in September: 4
The months with the highest UV index are May, 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
Mercersburg, PA
- Average cloud cover in September: 39
The months with the most cloud cover are January, February and December (Cloud cover 50).
The month with the least cloud cover is July (Cloud cover 31).
Average visibility in September
Mercersburg, PA
- Average visibility in September: 5mi
The months with the highest visibility are April, June, July and November (6mi).
The months with the lowest visibility are January, February, March, May, August, September, October and December (5mi).
