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September Weather in Brillion, United States

Last updated: June 24, 2025

In September, the average temperature in Brillion, United States hovers around 17°C (63°F), with minimums dipping to 1°C (35°F) and maximums soaring to 33°C (91°F). Be prepared for 69 mm (2.7 in) of precipitation spread over approximately 10 days, and a relatively high average humidity of 78%. Whether you’re basking in the warmth or bracing for a shower, make sure to dress accordingly!

September Temperature in Brillion

In September in Brillion, the average temperature is 17°C (63°F). Maximums can reach 33°C (91°F), while minimums can drop as low as 1°C (35°F). This varied climate makes Brillion an ideal destination for travelers seeking both warm days and cool evenings.

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

The chart illustrates September temperature patterns in Brillion, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Brillion, September typically has an average temperature of 17°C (63°F), with highs reaching up to 33°C (91°F) and lows dropping to around 1°C (35°F).
JanFebMarAprMayJunJulAugSepOctNovDec212133435668737063503627
Data source: Temperature data for Brillion 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 Brillion

In Brillion in September, the precipitation amount is 69 mm (2.7 in) spread over a period of 10 days.

September Precipitation Trends in Brillion

The chart displays monthly precipitation patterns in Brillion, 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 Brillion, September typically receives around 69 mm (2.7 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec4347589810410311010169974851
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Brillion

In Brillion in September, humidity is 78%. With an average temperature of 17°C (63°F), this humidity feels like a warm, enveloping blanket, making traveling slightly uncomfortable as you navigate the sticky air, prompting the need for frequent breaks in cooler, shaded areas.

September Average Humidity in Brillion

This chart illustrates the average monthly humidity levels in Brillion, 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 Brillion is approximately 78%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec89%90%87%84%77%75%75%73%78%84%89%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Brillion

In Brillion 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 Brillion.

Maximum UV Index Levels in Brillion for September

The chart shows the monthly maximum UV Index (UVI) for Brillion 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 Brillion typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec2457910997532
Data source: Brillion 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 Brillion Compares to Other Months

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

This table compares monthly weather conditions in Brillion, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-6°C (21°F)43 mm (1.7 inches)89%low
February Weather-6°C (21°F)47 mm (1.9 inches)90%moderate
March Weather1°C (34°F)58 mm (2.3 inches)87%moderate
April Weather6°C (43°F)98 mm (3.9 inches)84%high
May Weather14°C (57°F)104 mm (4.1 inches)77%very high
June Weather20°C (68°F)103 mm (4.1 inches)75%very high
July Weather23°C (73°F)110 mm (4.3 inches)74%very high
August Weather21°C (70°F)101 mm (4.0 inches)73%very high
September Weather17°C (63°F)69 mm (2.7 inches)78%high
October Weather10°C (50°F)97 mm (3.8 inches)84%moderate
November Weather2°C (36°F)48 mm (1.9 inches)89%moderate
December Weather-3°C (27°F)51 mm (2.0 inches)87%low

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