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September Weather in McLean, United States

Last updated: June 24, 2025

In September, the average temperature in McLean, United States hovers around 23°C (73°F), making it a pleasantly warm time to visit. Expect temperatures to fluctuate, with a minimum of 4°C (40°F) and a maximum soaring to 37°C (100°F). During this month, precipitation averages 50 mm (2.0 in), typically spread over 6 days, while the average humidity sits at a comfortable 72%.

September Temperature in McLean

In September in McLean, the average temperature is 23°C (73°F), with maximums that can reach 37°C (100°F) and minimums dropping as low as 4°C (40°F). This varied climate makes McLean an ideal destination for travelers seeking both warm days and cooler evenings.

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

The chart illustrates September temperature patterns in McLean, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In McLean, September typically has an average temperature of 23°C (73°F), with highs reaching up to 37°C (100°F) and lows dropping to around 4°C (40°F).
JanFebMarAprMayJunJulAugSepOctNovDec383951576877817973594842
Data source: Temperature data for McLean 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 McLean

In McLean in September, the precipitation amount is 50 mm (2.0 in) over the course of 6 days.

September Precipitation Trends in McLean

The chart displays monthly precipitation patterns in McLean, 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 McLean, September typically receives around 50 mm (2.0 inches) of precipitation spread over approximately 6 days.
JanFebMarAprMayJunJulAugSepOctNovDec231559368259364350691423
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in McLean

In McLean in September, humidity is 72%. With an average temperature of 23°C (73°F), this humidity feels like a warm embrace, making travel exhilarating yet slightly sticky, as the air clings to your skin and invites you to seek out cool, refreshing places to explore.

September Average Humidity in McLean

This chart illustrates the average monthly humidity levels in McLean, 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 McLean is approximately 72%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec75%76%64%70%78%81%82%78%72%73%81%81%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in McLean

In McLean in September, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in McLean.

Maximum UV Index Levels in McLean for September

The chart shows the monthly maximum UV Index (UVI) for McLean 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 McLean typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec468101112121110754
Data source: McLean 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 McLean Compares to Other Months

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

This table compares monthly weather conditions in McLean, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather3°C (38°F)23 mm (0.9 inches)75%moderate
February Weather4°C (39°F)15 mm (0.6 inches)76%high
March Weather11°C (51°F)59 mm (2.3 inches)64%very high
April Weather14°C (58°F)36 mm (1.4 inches)70%very high
May Weather20°C (68°F)82 mm (3.2 inches)78%extreme
June Weather25°C (77°F)59 mm (2.3 inches)81%extreme
July Weather27°C (81°F)36 mm (1.4 inches)82%extreme
August Weather26°C (79°F)43 mm (1.7 inches)78%extreme
September Weather23°C (73°F)50 mm (2.0 inches)72%very high
October Weather15°C (59°F)69 mm (2.7 inches)73%high
November Weather9°C (49°F)14 mm (0.5 inches)80%moderate
December Weather6°C (42°F)23 mm (0.9 inches)81%moderate

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