September weather forecastGreenwich, CT
September
Weather in September
With the arrival of September, Greenwich begins its transition from summer to fall. The foliage starts to change, painting the city with hues of autumn. The temperature also drops, signaling the impending colder months. Despite a decrease from August, the 3.5" (89mm) rainfall is relatively high for September. The sea temperature remains relatively warm, warranting one last dip before the cold sets in.Temperature
With the onset of September, Greenwich's climate undergoes a slight change as the average high-temperature moves from a warm 80.6°F (27°C) in August to a still moderately hot 73.4°F (23°C). Greenwich experiences a mean temperature of 61.7°F (16.5°C) during September nights.Humidity
In Greenwich, the average relative humidity in September is 74%.Rainfall
In Greenwich, in September, it is raining for 13.5 days, with typically 2.72" (69mm) of accumulated precipitation. Throughout the year, there are 165.6 rainfall days, and 37.64" (956mm) of precipitation is accumulated.Snowfall
May through October are months without snowfall.Ocean temperature
In Greenwich, in September, the average water temperature is 68.9°F (20.5°C).Note: For most, swimming in 68.9°F (20.5°C) is not an enjoyable activity. Furthermore, controlling your breathing becomes progressively more difficult as the water temperature decreases from 69.8°F (21°C) to 59°F (15°C).
Daylight
The average length of the day in September is 12h and 28min.On the first day of the month, sunrise is at 6:21 am and sunset at 7:26 pm. On the last day of September, sunrise is at 6:50 am and sunset at 6:37 pm EDT.
Sunshine
The average sunshine in September in Greenwich, Connecticut, is 8.8h.UV index
The average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a moderate health risk from exposure to the Sun's UV rays for the ordinary person.Note: The maximum daily UV index of 4 in September interprets into the following recommendations:
Prioritize safety - Recommendations to avert sunburn are shared. Considering the strength of solar radiation at midday, one should avoid direct Sun exposure. Equip yourself with UVA and UVB-filtering sunglasses on clear, sunny days.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Greenwich, CT
- Average high temperature in September: 73.4°F
The warmest month (with the highest average high temperature) is July (82°F).
The month with the lowest average high temperature is January (35.8°F).
- Average low temperature in September: 61.7°F
The month with the highest average low temperature is July (69.1°F).
The coldest month (with the lowest average low temperature) is January (26.1°F).
Average pressure in September
Greenwich, CT
- Average pressure in September: 30.05"Hg
The month with the highest atmospheric pressure is November (30.1"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in September
Greenwich, CT
- Average wind speed in September: 7.5mph
The windiest month (with the highest average wind speed) is January (9.9mph).
The calmest month (with the lowest average wind speed) is July (6.5mph).
Average humidity in September
Greenwich, CT
- Average humidity in September: 74%
The months with the highest relative humidity are February, May and December (75%).
The month with the lowest relative humidity is August (71%).
Average rainfall in September
Greenwich, CT
- Average rainfall in September: 2.72"
The wettest month (with the highest rainfall) is July (4.13").
The driest months (with the least rainfall) are January and February (2.4").
Average rainfall days in September
Greenwich, CT
- Average rainfall days in September: 13.5 days
The month with the highest number of rainy days is July (18.1 days).
The month with the least rainy days is January (7.9 days).
Average snowfall in September
Greenwich, CT
- Average snowfall in September: 0"
The month with the highest snowfall is February (2.52").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Greenwich, CT
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (7.2 days).
The months with the least snowfall days are June, July, August, September and October (0 days).
Average sea temperature in September
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
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 month with the least sunshine is February (Average sunshine: 4h and 42min).
Average sunshine days in September
Greenwich, CT
- Average sunshine days in September: 14.3 days
The month with the most sunshine days is November (17.8 days).
The month with the least sunshine days is June (10.7 days).
Average UV index in September
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
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
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).
