September Weather in Hillsboro, United States

Last updated: June 24, 2025

In Hillsboro, United States, the average temperature in September is a comfortable 18°C (64°F). However, you can expect a range, with minimums dipping to 2°C (36°F) and maximums soaring up to 33°C (92°F). Be prepared for some rain as well, with an average precipitation of 110 mm (4.3 in) spread over about 10 days. The air tends to be humid, with an average humidity level of 74%, so dress accordingly!

September Temperature in Hillsboro

In September in Hillsboro, the average temperature is 18°C (64°F), with maximums reaching 33°C (92°F) and minimums dropping as low as 2°C (36°F). This diverse temperature range makes Hillsboro an ideal destination for travelers seeking both warm and cooler experiences during their visit.

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 18°C (64°F), with highs reaching up to 33°C (92°F) and lows dropping to around 2°C (36°F).

Data source: Temperature data for Hillsboro generated using information from the Copernicus Climate Change Service.

September Precipitation in Hillsboro

In Hillsboro in September, the precipitation amount is 110 mm (4.3 in) over a period of 10 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 110 mm (4.3 inches) of precipitation spread over approximately 10 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

September Humidity in Hillsboro

In Hillsboro in September humidity is 74%. With an average temperature of 18°C (64°F), this humidity feels like a warm embrace, making it ideal for leisurely strolls but potentially uncomfortable for extended outdoor activities.

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 74%, offering insight into how humid the weather typically is during this month.

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.

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.
	Temperature	Precipitation	Humidity	UV
January Weather	-7°C (20°F)	41 mm (1.6 inches)	84%	low
February Weather	-6°C (21°F)	54 mm (2.1 inches)	85%	moderate
March Weather	1°C (35°F)	59 mm (2.3 inches)	84%	moderate
April Weather	7°C (45°F)	91 mm (3.6 inches)	83%	very high
May Weather	15°C (59°F)	137 mm (5.4 inches)	75%	very high
June Weather	21°C (70°F)	119 mm (4.7 inches)	79%	very high
July Weather	23°C (74°F)	107 mm (4.2 inches)	75%	very high
August Weather	21°C (70°F)	116 mm (4.6 inches)	69%	very high
September Weather	18°C (64°F)	110 mm (4.3 inches)	74%	very high
October Weather	10°C (50°F)	111 mm (4.4 inches)	79%	moderate
November Weather	2°C (35°F)	51 mm (2.0 inches)	88%	moderate
December Weather	-3°C (27°F)	46 mm (1.8 inches)	82%	low