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September Weather in Greenwich, United States

Last updated: June 24, 2025

In September, the average temperature in Greenwich, United States hovers around 20°C (67°F). However, be prepared for a range of temperatures, with minimums dipping to 4°C (40°F) and highs soaring up to 33°C (92°F). During this month, expect about 79 mm (3.1 in) of precipitation spread over approximately 10 days, while the average humidity lingers at a comfortable 78%.

September Temperature in Greenwich

In September in Greenwich, the average temperature is 20°C (67°F). The maximum can reach 33°C (92°F), and the minimum can be as low as 4°C (40°F). It's an ideal time for travelers to enjoy mild weather and explore both outdoor activities and cultural sites.

September Weather in Greenwich: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Greenwich, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Greenwich, September typically has an average temperature of 20°C (67°F), with highs reaching up to 33°C (92°F) and lows dropping to around 4°C (40°F).
JanFebMarAprMayJunJulAugSepOctNovDec293240506270747267564134
Data source: Temperature data for Greenwich generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Greenwich

In Greenwich in September, the precipitation amount is 79 mm (3.1 in) over a span of 10 days.

September Precipitation Trends in Greenwich

The chart displays monthly precipitation patterns in Greenwich, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Greenwich, September typically receives around 79 mm (3.1 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec7892971231291361289179968884
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Greenwich

In Greenwich in September humidity is 78%. With an average temperature of 20°C (67°F), this humidity feels like walking through a warm, thick blanket, making travel a bit sticky and requiring frequent breaks to find shade and cool refreshments.

September Average Humidity in Greenwich

This chart illustrates the average monthly humidity levels in Greenwich, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Greenwich is approximately 78%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec88%87%87%88%81%82%81%78%78%82%89%86%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Greenwich

In Greenwich in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Greenwich.

Maximum UV Index Levels in Greenwich for September

The chart shows the monthly maximum UV Index (UVI) for Greenwich in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Greenwich typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356810101098642
Data source: Greenwich September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How September Weather in Greenwich Compares to Other Months

Weather in Greenwich varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Greenwich, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Greenwich, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-2°C (29°F)78 mm (3.1 inches)88%moderate
February Weather0°C (32°F)92 mm (3.6 inches)87%moderate
March Weather4°C (40°F)97 mm (3.8 inches)87%high
April Weather10°C (50°F)123 mm (4.8 inches)87%very high
May Weather16°C (62°F)129 mm (5.1 inches)81%very high
June Weather21°C (71°F)136 mm (5.4 inches)82%very high
July Weather24°C (75°F)128 mm (5.0 inches)81%very high
August Weather22°C (72°F)91 mm (3.6 inches)78%very high
September Weather20°C (67°F)79 mm (3.1 inches)78%very high
October Weather14°C (57°F)96 mm (3.8 inches)82%high
November Weather5°C (41°F)88 mm (3.4 inches)89%moderate
December Weather1°C (35°F)84 mm (3.3 inches)86%low

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