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September Weather in Mount Vernon, United States

Last updated: June 24, 2025

In September, the average temperature in Mount Vernon, United States is a pleasant 23°C (73°F). Expect a minimum of 8°C (47°F) on cooler days and a maximum reaching up to 34°C (94°F) during warmer spells. The region sees about 64 mm (2.5 in) of precipitation spread over 7 days, contributing to an average humidity of 79%.

September Temperature in Mount Vernon

In September in Mount Vernon, the average temperature is 23°C (73°F), with maximums reaching 34°C (94°F) and minimums dropping to as low as 8°C (47°F). This pleasant climate makes it an ideal time for travelers to explore and enjoy outdoor activities.

September Weather in Mount Vernon: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Mount Vernon, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Mount Vernon, September typically has an average temperature of 23°C (73°F), with highs reaching up to 34°C (94°F) and lows dropping to around 8°C (47°F).
JanFebMarAprMayJunJulAugSepOctNovDec343748566877807773604540
Data source: Temperature data for Mount Vernon 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 Mount Vernon

In Mount Vernon in September, the precipitation amount is 64 mm (2.5 in) accumulated over a period of 7 days.

September Precipitation Trends in Mount Vernon

The chart displays monthly precipitation patterns in Mount Vernon, 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 Mount Vernon, September typically receives around 64 mm (2.5 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec931071431321651009486641219188
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Mount Vernon

In Mount Vernon in September humidity is 79%. With an average temperature of 23°C (73°F), this humidity feels like a warm embrace that clings to the skin, making travel feel both invigorating and slightly exhausting as the air wraps around you like a damp blanket.

September Average Humidity in Mount Vernon

This chart illustrates the average monthly humidity levels in Mount Vernon, 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 Mount Vernon is approximately 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%82%84%83%80%83%82%83%79%79%88%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Mount Vernon

In Mount Vernon in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Mount Vernon.

Maximum UV Index Levels in Mount Vernon for September

The chart shows the monthly maximum UV Index (UVI) for Mount Vernon 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 Mount Vernon typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3579111110109753
Data source: Mount Vernon 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 Mount Vernon Compares to Other Months

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

This table compares monthly weather conditions in Mount Vernon, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather1°C (34°F)93 mm (3.7 inches)84%moderate
February Weather3°C (38°F)107 mm (4.2 inches)82%moderate
March Weather9°C (48°F)143 mm (5.6 inches)84%high
April Weather14°C (57°F)131 mm (5.2 inches)83%very high
May Weather20°C (69°F)165 mm (6.5 inches)80%extreme
June Weather25°C (77°F)100 mm (3.9 inches)83%extreme
July Weather27°C (80°F)94 mm (3.7 inches)82%very high
August Weather25°C (77°F)86 mm (3.4 inches)82%very high
September Weather23°C (73°F)64 mm (2.5 inches)79%very high
October Weather16°C (61°F)121 mm (4.8 inches)79%high
November Weather7°C (45°F)91 mm (3.6 inches)88%moderate
December Weather5°C (41°F)88 mm (3.4 inches)87%moderate

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