September weather forecastOld Greenwich, CT
September
Weather in September
September in Old Greenwich signals the transition from warm summer to mild fall, with temperatures beginning to decrease slowly. The rainfall is comparatively lower at 2.68" (68mm), making room for clear skies and a refreshing breeze. The longer hours of sunlight still make it possible to spend the daytime outdoors, hence prolonging the summer fun for residents. The lower temperatures and weakening sunshine do not dampen residents' spirits as they continue to enjoy outdoor activities in autumn’s early arrival. It's an excellent time to explore the change in the city’s landscape and its charm.Temperature
September sees a slight reduction in average high-temperature, with a shift from a moderately hot 80.4°F (26.9°C) in August to an agreeable 73.2°F (22.9°C). Throughout the month of September, Old Greenwich witnesses an average low-temperature of 61.7°F (16.5°C).Humidity
The average relative humidity in September is 73%.Rainfall
In Old Greenwich, in September, it is raining for 13.3 days, with typically 2.68" (68mm) of accumulated precipitation. Throughout the year, in Old Greenwich, Connecticut, there are 166.6 rainfall days, and 38.07" (967mm) of precipitation is accumulated.Snowfall
In Old Greenwich, snow does not fall in May through October.Ocean temperature
In Old Greenwich, the average seawater temperature in September is 68.9°F (20.5°C).Note: For the majority of people, swimming in water at 68.9°F (20.5°C) is not enjoyable. The challenge of controlling breathing escalates as the temperature decreases from 69.8°F (21°C) to 59°F (15°C).
Daylight
In Old Greenwich, the average length of the day in September is 12h and 28min.On the first day of September, sunrise is at 6:21 am and sunset at 7:26 pm. On the last day of the month, sunrise is at 6:50 am and sunset at 6:37 pm EDT.
Sunshine
The average sunshine in September is 8.8h.UV index
In September, the average daily maximum UV index is 4. A UV Index estimate of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV radiation for average individuals.Note: In September, the maximum UV index of 4 transforms into these recommendations:
Be careful. Light complexion individuals might get burns in fewer than 30 minutes. The midday Sun can be harmful due to its potent UV radiation; seek shade and reduce exposure. Shield yourself from the harmful effects of UV radiation with sun-protective attire, a hat, and quality sunglasses.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Old Greenwich, CT
- Average high temperature in September: 73.2°F
The warmest month (with the highest average high temperature) is July (81.9°F).
The month with the lowest average high temperature is January (36°F).
- Average low temperature in September: 61.7°F
The month with the highest average low temperature is July (69.3°F).
The coldest month (with the lowest average low temperature) is January (26.2°F).
Average pressure in September
Old Greenwich, CT
- 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
Old Greenwich, CT
- Average wind speed in September: 7.6mph
The windiest month (with the highest average wind speed) is January (10.1mph).
The calmest month (with the lowest average wind speed) is July (6.6mph).
Average humidity in September
Old Greenwich, CT
- Average humidity in September: 73%
The months with the highest relative humidity are February, May, June and December (75%).
The month with the lowest relative humidity is August (71%).
Average rainfall in September
Old Greenwich, CT
- Average rainfall in September: 2.68"
The wettest month (with the highest rainfall) is July (4.13").
The driest month (with the least rainfall) is January (2.44").
Average rainfall days in September
Old Greenwich, CT
- Average rainfall days in September: 13.3 days
The month with the highest number of rainy days is July (17.8 days).
The month with the least rainy days is January (8.6 days).
Average snowfall in September
Old Greenwich, CT
- Average snowfall in September: 0"
The month with the highest snowfall is February (2.6").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Old Greenwich, CT
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (7.3 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average sea temperature in September
Old Greenwich, CT
- Average sea temperature in September: 68.9°F
The best month for swimming (with the highest average sea temperature) is August (73.1°F).
The coldest month (with the lowest average sea temperature) is February (39.5°F).
Average daylight in September /
Average sunshine in September
Old Greenwich, CT
- Average daylight in September: 12h and 30min
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 48min
The month with the most sunshine is July (Average sunshine: 10h and 30min).
The months with the least sunshine are February and December (Average sunshine: 4h and 42min).
Average sunshine days in September
Old Greenwich, CT
- Average sunshine days in September: 14.8 days
The month with the most sunshine days is November (17.9 days).
The month with the least sunshine days is June (11.1 days).
Average UV index in September
Old Greenwich, CT
- Average UV index in September: 4
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
Old Greenwich, CT
- Average cloud cover in September: 35
The month with the most cloud cover is December (Cloud cover 49).
The month with the least cloud cover is August (Cloud cover 31).
Average visibility in September
Old Greenwich, CT
- 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).
