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September Weather in Hillsboro, United States

Last updated: June 24, 2025

In September, the average temperature in Hillsboro, United States hovers around 21°C (69°F). Expect a range from a chilly 6°C (42°F) to a warm 35°C (94°F). During this time, precipitation typically reaches 96 mm (3.8 in) over about 8 days, while humidity levels average around 73%, creating a distinctly refreshing environment.

September Temperature in Hillsboro

In September in Hillsboro, the average temperature is 21°C (69°F), with maximum temperatures reaching up to 35°C (94°F) and minimums dropping as low as 6°C (42°F). This diverse temperature range makes Hillsboro an ideal destination for travelers seeking both warmth and cooler respite during their adventures.

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

The chart illustrates September temperature patterns in Hillsboro, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Hillsboro, September typically has an average temperature of 21°C (69°F), with highs reaching up to 35°C (94°F) and lows dropping to around 6°C (42°F).
JanFebMarAprMayJunJulAugSepOctNovDec323644536472767469584338
Data source: Temperature data for Hillsboro 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 Hillsboro

In Hillsboro in September, the precipitation amount is 96 mm (3.8 in) over the course of 8 days.

September Precipitation Trends in Hillsboro

The chart displays monthly precipitation patterns in Hillsboro, 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 Hillsboro, September typically receives around 96 mm (3.8 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec83111134130134140127899610397111
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Hillsboro

In Hillsboro in September, humidity is 73%. With an average temperature of 21°C (69°F), this humidity feels like a warm, sticky embrace, making outdoor activities somewhat stifling and travel a bit more challenging, as the air is dense and can leave you feeling fatigued more quickly.

September Average Humidity in Hillsboro

This chart illustrates the average monthly humidity levels in Hillsboro, 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 Hillsboro is approximately 73%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec88%88%87%85%81%82%81%73%73%78%89%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Hillsboro

In Hillsboro 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 Hillsboro.

Maximum UV Index Levels in Hillsboro for September

The chart shows the monthly maximum UV Index (UVI) for Hillsboro 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 Hillsboro typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec357910101098643
Data source: Hillsboro 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 Hillsboro Compares to Other Months

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

This table compares monthly weather conditions in Hillsboro, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather0°C (33°F)82 mm (3.2 inches)88%moderate
February Weather2°C (36°F)111 mm (4.4 inches)88%moderate
March Weather7°C (44°F)134 mm (5.3 inches)87%high
April Weather12°C (53°F)129 mm (5.1 inches)85%very high
May Weather18°C (65°F)134 mm (5.3 inches)81%very high
June Weather22°C (72°F)140 mm (5.5 inches)82%very high
July Weather24°C (76°F)126 mm (5.0 inches)81%very high
August Weather23°C (74°F)89 mm (3.5 inches)73%very high
September Weather21°C (69°F)96 mm (3.8 inches)73%very high
October Weather15°C (58°F)103 mm (4.1 inches)78%high
November Weather6°C (43°F)97 mm (3.8 inches)89%moderate
December Weather3°C (38°F)111 mm (4.4 inches)87%moderate

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