September weather forecast
Groton, CT

englishespañol中文
Share

Weather in September

September in Groton is a time of climatic subtlety when summer starts to fade into fall. The weather becomes noticeably cooler, especially during the evening and night hours. The sea temperatures begin to drop, indicating a gradual close to the beach and boating season. Rainfall records the lowest average of the year at 1.65" (42mm), making the city dry and arid. Groton welcomes the fall foliage, and the transition from summer to autumn is visually stunning.

Temperature

Transition into September in Groton subtly marks a drop in the average high-temperature, moderately moving from a moderately hot 77.7°F (25.4°C) in August to a pleasant 72°F (22.2°C). The low-temperature in Groton averages to a mild 59.9°F (15.5°C) during the nights of September.

Humidity

In September, the average relative humidity in Groton is 78%.

Rainfall

The month with the least rainfall is September, when the rain falls for 12 days and typically collects 1.65" (42mm) of precipitation.

Snowfall

In Groton, snow does not fall in May through October.

Ocean temperature

In Groton, the average seawater temperature in September is 68.2°F (20.1°C).
Note: Most people do not enjoy swimming in water that is 68.2°F (20.1°C). Breathing becomes increasingly challenging as the water temperature dips under 69.8°F (21°C).

Daylight

In September, the average length of the day is 12h and 28min.
On the first day of September, sunrise is at 6:15 am and sunset at 7:20 pm. On the last day of the month, sunrise is at 6:44 am and sunset at 6:31 pm EDT.

Sunshine

The average sunshine in September is 8.9h.

UV index

In September, the average daily maximum UV index is 4. A UV Index estimate of 3 to 5 represents a moderate threat to health from exposure to the Sun's UV radiation for average individuals.
Note: The UV index of 4 during September leads to these advisories:
Adopt protective measures - Requirement to safeguard skin and eyes from harm exists. When the Sun's UV radiation is most intense during midday, it's best to find shade and limit exposure. Wearing sunglasses with both UVA and UVB protection effectively reduces sun-induced eye damage.
[Resources]

Frequently asked questions

What is the usual temperature for Groton in September?

September temperatures in Groton, Connecticut, vary between a high-temperature of 72°F (22.2°C) and a low-temperature of 59.9°F (15.5°C).

What is the average humidity in September in Groton?

In September, the average relative humidity is 78%.

What is the driest month in Groton?

The month with the least rainfall in Groton, Connecticut, is September, when the rain falls for 12 days and typically collects 1.65" (42mm) of precipitation.

How many days does it rain in September in Groton?

In Groton, Connecticut, in September, it is raining for 12 days, with typically 1.65" (42mm) of accumulated precipitation.

When it does not snow in Groton?

May through October are months without snowfall in Groton.

What is the ocean temperature in September in Groton?

In Groton, in September, the average water temperature is 68.2°F (20.1°C). For most, swimming in 68.2°F (20.1°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).

How many hours of daylight does Groton have in September?

In September, the average day length in Groton is 12h and 28min.

When is the sunrise / sunset in September in Groton?

On the first day of September in Groton, Connecticut, sunrise is at 6:15 am and sunset at 7:20 pm. On the last day of the month, sunrise is at 6:44 am and sunset at 6:31 pm EDT.

How long on average sun shines in September in Groton?

The average sunshine duration in September in Groton, Connecticut, is 8.9h.

How high is the UV index in September in Groton?

The average daily maximum UV index in September in Groton, Connecticut, is 4. A UV Index of 3 to 5 symbolizes a medium hazard to health from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Groton, CT

Average temperature in September - Groton, CT
  • Average high temperature in September: 72°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 (36.1°F).

  • Average low temperature in September: 59.9°F

The month with the highest average low temperature is July (66.7°F).
The coldest month (with the lowest average low temperature) is January (26.2°F).

[Resources]

Average pressure in September
Groton, CT

Average pressure in September - Groton, CT
  • Average pressure in September: 30.05"Hg

The month with the highest atmospheric pressure is November (30.08"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).

[Resources]

Average wind speed in September
Groton, CT

Average wind speed in September - Groton, CT
  • Average wind speed in September: 8.8mph

The windiest month (with the highest average wind speed) is January (11.9mph).
The calmest months (with the lowest average wind speed) are July and August (7.8mph).

[Resources]

Average humidity in September
Groton, CT

Average humidity in September - Groton, CT
  • Average humidity in September: 78%

The month with the highest relative humidity is June (80%).
The months with the lowest relative humidity are January, March, April and November (74%).

[Resources]

Average rainfall in September
Groton, CT

Average rainfall in September - Groton, CT
  • Average rainfall in September: 1.65"

The wettest month (with the highest rainfall) is December (3.86").
The driest month (with the least rainfall) is September (1.65").

[Resources]

Average rainfall days in September
Groton, CT

Average rainfall days in September - Groton, CT
  • Average rainfall days in September: 12 days

The month with the highest number of rainy days is July (15.8 days).
The month with the least rainy days is February (9.5 days).

[Resources]

Average snowfall in September
Groton, CT

Average snowfall in September - Groton, CT
  • Average snowfall in September: 0"

The month with the highest snowfall is March (2.56").
The months with the least snowfall are May, June, July, August, September and October (0").

[Resources]

Average snowfall days in September
Groton, CT

Average snowfall days in September - Groton, CT
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is February (6.8 days).
The months with the least snowfall days are June, July, August, September and October (0 days).

[Resources]

Average sea temperature in September
Groton, CT

Average sea temperature in September - Groton, CT
  • Average sea temperature in September: 68.2°F

The best month for swimming (with the highest average sea temperature) is August (72.1°F).
The coldest month (with the lowest average sea temperature) is February (38.8°F).

[Resources]

Average daylight in September /
Average sunshine in September
Groton, CT

Average daylight in September / Average sunshine in September - Groton, CT
  • 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 12min).

  • Average sunshine in September: 8h and 5min

The month with the most sunshine is August (Average sunshine: 10h and 36min).
The months with the least sunshine are February and December (Average sunshine: 4h and 54min).

[Resources]

Average sunshine days in September
Groton, CT

Average sunshine days in September - Groton, CT
  • Average sunshine days in September: 15.8 days

The month with the most sunshine days is November (16.5 days).
The month with the least sunshine days is February (12.5 days).

[Resources]

Average UV index in September
Groton, CT

Average UV index in September - Groton, 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).

[Resources]

Average cloud cover in September
Groton, CT

Average cloud cover in September - Groton, CT
  • Average cloud cover in September: 33

The months with the most cloud cover are February, March and December (Cloud cover 47).
The month with the least cloud cover is August (Cloud cover 29).

[Resources]

Average visibility in September
Groton, CT

Average visibility in September - Groton, 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).

[Resources]

Groton, Connecticut, USA

Weather forecast for your location

1. Click Locate me button
2. Allow the app to use your location