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September Weather in Brown Deer, United States

Last updated: June 24, 2025

In September, the average temperature in Brown Deer, United States hovers around 18°C (65°F). Expect cool nights with a minimum of 5°C (41°F), while daytime highs can reach up to 29°C (85°F). This month typically sees 100 mm (3.9 in) of precipitation spread over about 10 days, accompanied by a notable 79% average humidity, creating a refreshing atmosphere.

September Temperature in Brown Deer

In September in Brown Deer, the average temperature is 18°C (65°F). Maximums can reach 29°C (85°F), and minimums can drop as low as 5°C (41°F). This range makes Brown Deer a comfortable destination for travelers, offering pleasant conditions for outdoor activities.

September Weather in Brown Deer: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Brown Deer, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Brown Deer, September typically has an average temperature of 18°C (65°F), with highs reaching up to 29°C (85°F) and lows dropping to around 5°C (41°F).
JanFebMarAprMayJunJulAugSepOctNovDec242535435364727165523831
Data source: Temperature data for Brown Deer 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 Brown Deer

In Brown Deer in September, the precipitation amount is 100 mm (3.9 in) over a span of 10 days.

September Precipitation Trends in Brown Deer

The chart displays monthly precipitation patterns in Brown Deer, 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 Brown Deer, September typically receives around 100 mm (3.9 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec59576810813110188771001195252
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Brown Deer

In Brown Deer in September, humidity is 79%. With an average temperature of 18°C (65°F), this humidity feels like walking through a warm mist, making traveling slightly uncomfortable and sticky, but offering a refreshing escape when you find moments of shade or a breeze.

September Average Humidity in Brown Deer

This chart illustrates the average monthly humidity levels in Brown Deer, 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 Brown Deer is approximately 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%85%85%85%78%80%78%76%79%83%88%82%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Brown Deer

In Brown Deer in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Brown Deer.

Maximum UV Index Levels in Brown Deer for September

The chart shows the monthly maximum UV Index (UVI) for Brown Deer 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 Brown Deer typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec24589101097532
Data source: Brown Deer 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 Brown Deer Compares to Other Months

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

This table compares monthly weather conditions in Brown Deer, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-4°C (24°F)59 mm (2.3 inches)85%low
February Weather-4°C (25°F)57 mm (2.2 inches)85%moderate
March Weather2°C (35°F)68 mm (2.7 inches)85%moderate
April Weather6°C (43°F)108 mm (4.3 inches)85%very high
May Weather12°C (54°F)131 mm (5.2 inches)78%very high
June Weather18°C (65°F)101 mm (4.0 inches)80%very high
July Weather22°C (72°F)88 mm (3.5 inches)78%very high
August Weather22°C (71°F)77 mm (3.0 inches)76%very high
September Weather18°C (65°F)100 mm (3.9 inches)79%high
October Weather11°C (53°F)119 mm (4.7 inches)83%moderate
November Weather3°C (38°F)52 mm (2.1 inches)88%moderate
December Weather0°C (32°F)52 mm (2.1 inches)81%low

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