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September Weather in Frederick, United States

Last updated: June 24, 2025

The average temperature in Frederick, United States during September is a pleasant 21°C (70°F). However, temperatures can vary significantly, with minimums dropping to 4°C (40°F) and maximums soaring up to 35°C (94°F). Expect around 107 mm (4.2 in) of precipitation spread over 9 days, contributing to an average humidity level of 68%.

September Temperature in Frederick

In September in Frederick, the average temperature is 21°C (70°F), with maximums reaching 35°C (94°F) and minimums dropping to as low as 4°C (40°F). Travelers should be prepared for a wide range of temperatures during their visit, ensuring they pack accordingly for both warm and cool conditions.

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

The chart illustrates September temperature patterns in Frederick, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Frederick, September typically has an average temperature of 21°C (70°F), with highs reaching up to 35°C (94°F) and lows dropping to around 4°C (40°F).
JanFebMarAprMayJunJulAugSepOctNovDec353944556473797670604538
Data source: Temperature data for Frederick 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 Frederick

In Frederick in September, the precipitation amount is 107 mm (4.2 in), occurring over a span of 9 days.

September Precipitation Trends in Frederick

The chart displays monthly precipitation patterns in Frederick, 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 Frederick, September typically receives around 107 mm (4.2 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec619590100134111138114107998894
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Frederick

In Frederick in September humidity is 68%. With an average temperature of 21°C (70°F), this humidity feels like a warm embrace, making the air feel slightly heavy and sticky, which can be quite exhausting for travelers.

September Average Humidity in Frederick

This chart illustrates the average monthly humidity levels in Frederick, 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 Frederick is approximately 68%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%86%86%84%78%79%70%59%68%80%87%85%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Frederick

In Frederick 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 Frederick.

Maximum UV Index Levels in Frederick for September

The chart shows the monthly maximum UV Index (UVI) for Frederick 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 Frederick typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec357910101098743
Data source: Frederick 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 Frederick Compares to Other Months

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

This table compares monthly weather conditions in Frederick, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather2°C (35°F)61 mm (2.4 inches)86%moderate
February Weather4°C (39°F)95 mm (3.7 inches)86%moderate
March Weather7°C (44°F)90 mm (3.6 inches)86%high
April Weather13°C (55°F)100 mm (3.9 inches)84%very high
May Weather18°C (65°F)134 mm (5.3 inches)78%very high
June Weather23°C (73°F)111 mm (4.4 inches)79%very high
July Weather26°C (79°F)138 mm (5.4 inches)70%very high
August Weather24°C (76°F)114 mm (4.5 inches)59%very high
September Weather21°C (70°F)107 mm (4.2 inches)68%very high
October Weather16°C (60°F)99 mm (3.9 inches)80%high
November Weather7°C (45°F)88 mm (3.5 inches)86%moderate
December Weather4°C (39°F)94 mm (3.7 inches)85%moderate

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