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 sea temperature 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
September sees a slight reduction in average high-temperature, with a shift from a warm 78.4°F (25.8°C) in August to a pleasant 72.3°F (22.4°C). Stony Brook's nighttime temperature in September experiences a slight dip from daytime highs, falling to an average of 64.8°F (18.2°C).Humidity
The average relative humidity in September is 74%.Rainfall
In Stony Brook, in September, it is raining for 12.6 days, with typically 2.4" (61mm) of accumulated precipitation. In Stony Brook, during the entire year, the rain falls for 146.8 days and collects up to 33.78" (858mm) of precipitation.Snowfall
April through September are months without snowfall.Ocean temperature
In September, the average ocean temperature is 69.6°F (20.9°C).Note: The majority of individuals find it unpleasurable to swim in 69.6°F (20.9°C). It becomes progressively harder to manage one's breathing as the water temperature falls below 69.8°F (21°C).
Daylight
In September, the average length of the day is 12h and 27min.On the first day of the month, sunrise is at 6:20 am and sunset at 7:24 pm. On the last day of September, sunrise is at 6:48 am and sunset at 6:35 pm EDT.
Sunshine
The average sunshine in September is 8.9h.UV index
In September, the average daily maximum UV index is 5. A UV Index reading of 3 to 5 represents a medium health hazard from exposure to the Sun's UV rays for average individuals.Note: The UV index of 5 during September leads to these advisories:
Ensure safety - Recommendations to avert sunburn are presented. The Sun is most powerful around mid-day, so it's a good practice to reduce direct exposure. Combat UV radiation's detrimental effects with sun-safe clothing and UV-blocking eyewear.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the usual temperature for Stony Brook in September?
What is the average humidity in September?
How much does it rain in September?
When it does not snow?
Does it snow in September?
How cold is the water in September?
How many hours of daylight does Stony Brook have in September?
When is the sunrise / sunset in September?
How long on average sun shines in September in Stony Brook?
What is the UV index reading in September?
Average temperature in September
Stony Brook, NY
- Average high temperature in September: 72.3°F
The warmest month (with the highest average high temperature) is July (79.2°F).
The month with the lowest average high temperature is January (37.6°F).
- Average low temperature in September: 64.8°F
The months with the highest average low temperature are July and August (71.1°F).
The coldest month (with the lowest average low temperature) is January (29.1°F).
Average pressure in September
Stony Brook, NY
- Average pressure in September: 30.05"Hg
The month with the highest atmospheric pressure is November (30.09"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in September
Stony Brook, NY
- Average wind speed in September: 9.8mph
The windiest month (with the highest average wind speed) is January (12.9mph).
The calmest month (with the lowest average wind speed) is July (8.3mph).
Average humidity in September
Stony Brook, NY
- Average humidity in September: 74%
The months with the highest relative humidity are May and June (77%).
The month with the lowest relative humidity is November (71%).
Average rainfall in September
Stony Brook, NY
- Average rainfall in September: 2.4"
The wettest month (with the highest rainfall) is December (3.58").
The driest month (with the least rainfall) is January (2.05").
Average rainfall days in September
Stony Brook, NY
- Average rainfall days in September: 12.6 days
The month with the highest number of rainy days is July (16.5 days).
The month with the least rainy days is January (6.8 days).
Average snowfall in September
Stony Brook, NY
- Average snowfall in September: 0"
The month with the highest snowfall is March (2.13").
The months with the least snowfall are April, May, June, July, August and September (0").
Average snowfall days in September
Stony Brook, NY
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (4.4 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average sea temperature in September
Stony Brook, NY
- Average sea temperature in September: 69.6°F
The best month for swimming (with the highest average sea temperature) is August (74°F).
The coldest month (with the lowest average sea temperature) is February (39.7°F).
Average daylight in September /
Average sunshine in September
Stony Brook, NY
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 6min).
The month with the shortest days is December (Average daylight: 9h and 18min).
- Average sunshine in September: 8h and 5min
The month with the most sunshine is July (Average sunshine: 10h and 36min).
The month with the least sunshine is February (Average sunshine: 4h and 42min).
Average sunshine days in September
Stony Brook, NY
- Average sunshine days in September: 15.7 days
The month with the most sunshine days is November (20.5 days).
The month with the least sunshine days is July (13 days).
Average UV index in September
Stony Brook, NY
- Average UV index in September: 5
The months with the highest UV index are June, July and August (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
Stony Brook, NY
- Average cloud cover in September: 33
The month with the most cloud cover is December (Cloud cover 49).
The month with the least cloud cover is August (Cloud cover 28).
Average visibility in September
Stony Brook, NY
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Stony Brook, New York, USA
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