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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 20°C (68°F). You can expect minimums around 5°C (41°F) and maximums soaring to 33°C (92°F). With an average precipitation of 83 mm (3.3 in) spread over about 10 days, don't forget your umbrella! Plus, the average humidity sits at a comfortable 78%, making it a delightful time to explore the area.

September Temperature in Mount Vernon

In September in Mount Vernon, the average temperature is 20°C (68°F), with maximums reaching 33°C (92°F) and minimums dropping as low as 5°C (41°F). This climate makes Mount Vernon an ideal destination for travelers seeking a pleasant mix of warm days and cool nights.

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 20°C (68°F), with highs reaching up to 33°C (92°F) and lows dropping to around 5°C (41°F).
JanFebMarAprMayJunJulAugSepOctNovDec303341516371757268574135
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 total precipitation amount is 83 mm (3.3 in) over a span of 10 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 83 mm (3.3 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec8310210813012514011583831009697
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 78%. With an average temperature of 20°C (68°F), this humidity feels like a warm, enveloping blanket that makes exploring the sights a bit sticky, so travelers should stay hydrated and take frequent breaks in the shade.

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 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 Mount Vernon

In Mount Vernon 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 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 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356910101098642
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 Weather-1°C (30°F)83 mm (3.3 inches)88%moderate
February Weather0°C (33°F)102 mm (4.0 inches)87%moderate
March Weather5°C (41°F)108 mm (4.2 inches)87%high
April Weather10°C (51°F)130 mm (5.1 inches)87%very high
May Weather17°C (63°F)124 mm (4.9 inches)81%very high
June Weather22°C (71°F)140 mm (5.5 inches)82%very high
July Weather24°C (75°F)115 mm (4.5 inches)81%very high
August Weather22°C (73°F)83 mm (3.3 inches)78%very high
September Weather20°C (68°F)83 mm (3.3 inches)78%very high
October Weather14°C (57°F)100 mm (4.0 inches)82%high
November Weather5°C (41°F)96 mm (3.8 inches)89%moderate
December Weather2°C (35°F)97 mm (3.8 inches)86%low

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