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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 27°C (80°F). Expect a range from a cool 10°C (51°F) to a sweltering 39°C (102°F). With an average precipitation of 77 mm (3.1 in) spread over 7 days, you might want to keep your umbrella handy! The air is moderately humid, with an average humidity level of 69%, making for a warm and occasionally rainy climate.

September Temperature in Hillsboro

In September in Hillsboro, the average temperature is 27°C (80°F). Maximums can reach 39°C (102°F), while minimums can drop as low as 10°C (51°F). It's advisable to pack for both warm days and cooler nights for your trip.

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 27°C (80°F), with highs reaching up to 39°C (102°F) and lows dropping to around 10°C (51°F).
JanFebMarAprMayJunJulAugSepOctNovDec485061667582868680695853
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 total precipitation amount is 77 mm (3.1 in) over the course of 7 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 77 mm (3.1 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec598685102176705591781314457
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 69%. With an average temperature of 27°C (80°F), this humidity feels like a warm embrace that can leave you feeling sticky and lethargic, making it essential to stay hydrated and take frequent breaks while exploring.

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 69%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec80%80%78%79%81%77%71%67%69%73%82%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 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 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 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec478101111111110864
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 Weather9°C (49°F)59 mm (2.3 inches)79%moderate
February Weather10°C (51°F)86 mm (3.4 inches)80%high
March Weather16°C (62°F)85 mm (3.3 inches)78%very high
April Weather19°C (67°F)102 mm (4.0 inches)79%very high
May Weather24°C (75°F)176 mm (6.9 inches)81%extreme
June Weather28°C (82°F)70 mm (2.8 inches)77%extreme
July Weather30°C (86°F)55 mm (2.2 inches)71%extreme
August Weather30°C (86°F)91 mm (3.6 inches)67%extreme
September Weather27°C (80°F)77 mm (3.1 inches)69%very high
October Weather21°C (69°F)131 mm (5.2 inches)73%very high
November Weather14°C (58°F)44 mm (1.7 inches)82%high
December Weather12°C (53°F)56 mm (2.2 inches)87%moderate

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