Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
The start of September signals a gentle decrease in the average high-temperature, transitioning from a moderately hot 76.5°F (24.7°C) in August to an agreeable 69.1°F (20.6°C). During September, the average low-temperature is recorded at a frosty 49.3°F (9.6°C).Humidity
In Williamstown, the average relative humidity in September is 81%.Rainfall
In Williamstown, Massachusetts, in September, during 12.9 rainfall days, 2.72" (69mm) of precipitation is typically accumulated. Throughout the year, in Williamstown, there are 167.1 rainfall days, and 35.98" (914mm) of precipitation is accumulated.Snowfall
June through September are months without snowfall in Williamstown.Daylight
In September, the average length of the day is 12h and 29min.On the first day of the month, sunrise is at 6:18 am and sunset at 7:26 pm. On the last day of September, sunrise is at 6:49 am and sunset at 6:35 pm EDT.
Sunshine
In September, the average sunshine is 8.3h.UV index
In September, the average daily maximum UV index is 3. A UV Index reading of 3 to 5 represents a moderate health risk from unprotected exposure to Sun's UV rays for average individuals.Note: The daily maximum UV index of 3 in September interprets into the following advice:
Heed the precautions - Suggestions to avoid sunburn are made. The Sun is most powerful around mid-day, so it's a good practice to reduce direct exposure. To cut down UV radiation exposure by about half, sport a wide-brim hat.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the average September temperature?
What is the average humidity in September?
How much does it rain in September?
When it does not snow?
Does it snow in September?
What is the average length of the day in September?
When are sunrise and sunset in September?
How many hours of sunshine does Williamstown have in September?
How high is the UV index in September?
Average temperature in September
Williamstown, MA
- Average high temperature in September: 69.1°F
The warmest month (with the highest average high temperature) is July (78.6°F).
The month with the lowest average high temperature is January (27°F).
- Average low temperature in September: 49.3°F
The month with the highest average low temperature is July (57°F).
The coldest month (with the lowest average low temperature) is January (14.7°F).
Average pressure in September
Williamstown, MA
- Average pressure in September: 30.06"Hg
The month with the highest atmospheric pressure is November (30.09"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed in September
Williamstown, MA
- Average wind speed in September: 5.5mph
The windiest months (with the highest average wind speed) are January and February (8.8mph).
The calmest month (with the lowest average wind speed) is August (5.3mph).
Average humidity in September
Williamstown, MA
- Average humidity in September: 81%
The month with the highest relative humidity is February (86%).
The month with the lowest relative humidity is April (77%).
Average rainfall in September
Williamstown, MA
- Average rainfall in September: 2.72"
The wettest month (with the highest rainfall) is October (3.62").
The driest month (with the least rainfall) is March (2.6").
Average rainfall days in September
Williamstown, MA
- Average rainfall days in September: 12.9 days
The month with the highest number of rainy days is July (17.8 days).
The month with the least rainy days is February (7.8 days).
Average snowfall in September
Williamstown, MA
- Average snowfall in September: 0"
The month with the highest snowfall is February (10").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Williamstown, MA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (15.8 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, MA
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 18min).
The month with the shortest days is December (Average daylight: 9h and 6min).
- Average sunshine in September: 8h and 2min
The month with the most sunshine is July (Average sunshine: 9h and 54min).
The month with the least sunshine is February (Average sunshine: 3h and 24min).
Average sunshine days in September
Williamstown, MA
- Average sunshine days in September: 14.3 days
The month with the most sunshine days is September (14.3 days).
The month with the least sunshine days is February (9 days).
Average UV index in September
Williamstown, MA
- Average UV index in September: 3
The months with the highest UV index are June, July and August (UV index 5).
The months with the lowest UV index are February and December (UV index 1).
Average cloud cover in September
Williamstown, MA
- Average cloud cover in September: 41
The month with the most cloud cover is February (Cloud cover 64).
The months with the least cloud cover are July and August (Cloud cover 38).
Average visibility in September
Williamstown, MA
- Average visibility in September: 5mi
The months with the highest visibility are January, March, April, May, June, July, August, September, October, November and December (5mi).
The month with the lowest visibility is February (4mi).
Williamstown, Massachusetts, USA
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