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September Weather in Swansea, United States

Last updated: June 24, 2025

In September, the average temperature in Swansea, United States hovers around 19°C (67°F), with temperatures ranging from a cool minimum of 6°C (43°F) to a warm maximum of 33°C (91°F). Visitors can expect about 97 mm (3.8 in) of precipitation spread over 9 days, complemented by an average humidity of 75%. Be prepared for a mix of pleasant warmth and occasional showers!

September Temperature in Swansea

In September in Swansea, the average temperature is 19°C (67°F). Maximum temperatures can reach up to 33°C (91°F), while the minimum can drop to as low as 6°C (43°F). This weather makes Swansea a perfect destination for travelers seeking both warm days and cool evenings.

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

The chart illustrates September temperature patterns in Swansea, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Swansea, September typically has an average temperature of 19°C (67°F), with highs reaching up to 33°C (91°F) and lows dropping to around 6°C (43°F).
JanFebMarAprMayJunJulAugSepOctNovDec333539485868747367574536
Data source: Temperature data for Swansea 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 Swansea

In Swansea in September, the total precipitation amount reaches 97 mm (3.8 in) over the course of 9 days.

September Precipitation Trends in Swansea

The chart displays monthly precipitation patterns in Swansea, 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 Swansea, September typically receives around 97 mm (3.8 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec7492102123101971229297135101120
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Swansea

In Swansea in September humidity is 75%. With an average temperature of 19°C (67°F), this humidity feels like a warm embrace, making travel invigorating yet slightly sticky, as you navigate through the vibrant streets or scenic landscapes.

September Average Humidity in Swansea

This chart illustrates the average monthly humidity levels in Swansea, 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 Swansea is approximately 75%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%84%82%79%75%78%76%76%76%75%80%80%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Swansea

In Swansea 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 Swansea.

Maximum UV Index Levels in Swansea for September

The chart shows the monthly maximum UV Index (UVI) for Swansea 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 Swansea typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3568910998642
Data source: Swansea 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 Swansea Compares to Other Months

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

This table compares monthly weather conditions in Swansea, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather0°C (33°F)74 mm (2.9 inches)84%moderate
February Weather1°C (35°F)92 mm (3.6 inches)84%moderate
March Weather4°C (39°F)102 mm (4.0 inches)82%high
April Weather9°C (49°F)123 mm (4.9 inches)79%very high
May Weather15°C (58°F)101 mm (4.0 inches)75%very high
June Weather20°C (68°F)97 mm (3.8 inches)78%very high
July Weather23°C (74°F)122 mm (4.8 inches)76%very high
August Weather23°C (74°F)92 mm (3.6 inches)76%very high
September Weather19°C (67°F)97 mm (3.8 inches)75%very high
October Weather14°C (57°F)135 mm (5.3 inches)75%high
November Weather7°C (45°F)101 mm (4.0 inches)80%moderate
December Weather2°C (36°F)120 mm (4.7 inches)80%low

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