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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 21°C (71°F). However, temperatures can vary significantly, with a minimum of 5°C (42°F) and a maximum soaring to 35°C (96°F). This month also brings 62 mm (2.4 in) of precipitation, typically spread over 6 days, contributing to an average humidity of 80%. Prepare for a mix of warm days and refreshing rains!

September Temperature in McLean

In September in McLean, the average temperature is 21°C (71°F). Maximums can reach 35°C (96°F), while minimums can drop to as low as 5°C (42°F). It's an ideal time for travelers seeking pleasant weather, but be prepared for both warmth 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 21°C (71°F), with highs reaching up to 35°C (96°F) and lows dropping to around 5°C (42°F).
JanFebMarAprMayJunJulAugSepOctNovDec283043526574777470574135
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 62 mm (2.4 in), spread 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 62 mm (2.4 inches) of precipitation spread over approximately 6 days.
JanFebMarAprMayJunJulAugSepOctNovDec677012112315012311496621156554
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 80%. With an average temperature of 21°C (71°F), this humidity feels like a warm, heavy blanket wrapping around you, making outdoor activities feel more exhausting and requiring frequent breaks to stay hydrated.

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 80%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%83%84%85%79%82%80%81%80%82%88%84%
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 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 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 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec357910111098642
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 Weather-2°C (28°F)67 mm (2.7 inches)82%moderate
February Weather-1°C (31°F)70 mm (2.7 inches)83%moderate
March Weather6°C (43°F)121 mm (4.8 inches)84%high
April Weather11°C (52°F)123 mm (4.8 inches)85%very high
May Weather18°C (65°F)150 mm (5.9 inches)79%very high
June Weather23°C (74°F)123 mm (4.8 inches)82%extreme
July Weather25°C (77°F)114 mm (4.5 inches)80%very high
August Weather23°C (74°F)96 mm (3.8 inches)81%very high
September Weather21°C (71°F)62 mm (2.4 inches)80%very high
October Weather14°C (57°F)115 mm (4.5 inches)82%high
November Weather5°C (41°F)65 mm (2.6 inches)88%moderate
December Weather2°C (35°F)54 mm (2.1 inches)84%low

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