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September Weather in Frederick, United States

Last updated: June 24, 2025

In September, the average temperature in Frederick, United States hovers around 25°C (77°F). However, be prepared for a temperature range that can dip as low as 8°C (46°F) and soar up to 38°C (101°F). During this period, expect about 86 mm (3.4 in) of rainfall spread over 7 days, along with an average humidity of 64%.

September Temperature in Frederick

In September in Frederick, the average temperature is 25°C (77°F). Maximum temperatures can reach 38°C (101°F), while the minimum can drop to as low as 8°C (46°F). It's an ideal time for travelers to enjoy a range of outdoor activities while being prepared for both warm days and cooler nights.

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 25°C (77°F), with highs reaching up to 38°C (101°F) and lows dropping to around 8°C (46°F).
JanFebMarAprMayJunJulAugSepOctNovDec414356627281858477645246
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 total precipitation amount is 86 mm (3.4 in) over a span of 7 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 86 mm (3.4 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec3530699811558283786692229
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 64%. With an average temperature of 25°C (77°F), this humidity feels like a warm embrace, making outdoor excursions feel a bit heavier, yet still inviting for travelers seeking a vibrant atmosphere.

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 64%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec76%76%70%72%82%82%80%72%64%71%81%84%
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 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 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 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec468101111121110854
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 Weather5°C (41°F)35 mm (1.4 inches)76%moderate
February Weather6°C (43°F)30 mm (1.2 inches)76%high
March Weather13°C (56°F)69 mm (2.7 inches)70%very high
April Weather17°C (62°F)98 mm (3.9 inches)72%very high
May Weather22°C (72°F)115 mm (4.5 inches)82%extreme
June Weather27°C (81°F)58 mm (2.3 inches)82%extreme
July Weather29°C (85°F)28 mm (1.1 inches)80%extreme
August Weather29°C (84°F)37 mm (1.5 inches)72%extreme
September Weather25°C (77°F)86 mm (3.4 inches)64%very high
October Weather18°C (64°F)69 mm (2.7 inches)71%very high
November Weather11°C (52°F)22 mm (0.9 inches)81%moderate
December Weather8°C (46°F)29 mm (1.1 inches)84%moderate

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