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September Weather in Guernsey, United States

Last updated: June 24, 2025

In September, the average temperature in Guernsey, United States hovers around 19°C (66°F). However, temperatures can fluctuate significantly, with a minimum as low as -2°C (29°F) and soaring to a maximum of 39°C (103°F). Expect some rain, as 24 mm (0.9 in) of precipitation is typical over 4 days, while the average humidity remains high at 76%.

September Temperature in Guernsey

In September in Guernsey, the average temperature is 19°C (66°F). Maximums can reach 39°C (103°F), while minimums can dip as low as -2°C (29°F). Therefore, it's essential to pack for a wide range of temperatures when traveling during this month.

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

The chart illustrates September temperature patterns in Guernsey, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Guernsey, September typically has an average temperature of 19°C (66°F), with highs reaching up to 39°C (103°F) and lows dropping to around -2°C (29°F).
JanFebMarAprMayJunJulAugSepOctNovDec312839465570767465474033
Data source: Temperature data for Guernsey 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 Guernsey

In Guernsey in September, the precipitation amount is 24 mm (0.9 in) over a period of 4 days.

September Precipitation Trends in Guernsey

The chart displays monthly precipitation patterns in Guernsey, 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 Guernsey, September typically receives around 24 mm (0.9 inches) of precipitation spread over approximately 4 days.
JanFebMarAprMayJunJulAugSepOctNovDec122350458537271624331717
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Guernsey

In Guernsey in September, humidity is 76%. With an average temperature of 19°C (66°F), this humidity feels like a warm, thick blanket wrapping around you, making travel mildly uncomfortable and encouraging frequent breaks in shaded or air-conditioned areas.

September Average Humidity in Guernsey

This chart illustrates the average monthly humidity levels in Guernsey, 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 Guernsey is approximately 76%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec73%78%64%66%74%84%85%85%76%71%73%75%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Guernsey

In Guernsey 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 Guernsey.

Maximum UV Index Levels in Guernsey for September

The chart shows the monthly maximum UV Index (UVI) for Guernsey 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 Guernsey typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec35710101111108643
Data source: Guernsey 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 Guernsey Compares to Other Months

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

This table compares monthly weather conditions in Guernsey, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-1°C (31°F)12 mm (0.5 inches)73%moderate
February Weather-2°C (29°F)23 mm (0.9 inches)78%moderate
March Weather4°C (39°F)50 mm (2.0 inches)64%high
April Weather8°C (46°F)45 mm (1.8 inches)66%very high
May Weather13°C (55°F)85 mm (3.3 inches)74%very high
June Weather21°C (70°F)37 mm (1.5 inches)84%extreme
July Weather25°C (77°F)27 mm (1.1 inches)85%extreme
August Weather23°C (74°F)16 mm (0.6 inches)85%very high
September Weather19°C (66°F)24 mm (0.9 inches)76%very high
October Weather8°C (47°F)33 mm (1.3 inches)71%high
November Weather4°C (40°F)17 mm (0.7 inches)73%moderate
December Weather1°C (33°F)17 mm (0.7 inches)75%moderate

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