September Weather in Rancho Cucamonga, United States

Last updated: June 24, 2025

In September, the average temperature in Rancho Cucamonga, United States hovers around 24°C (76°F), with a minimum drop to 11°C (52°F) and occasional peaks reaching up to 46°C (115°F). Visitors can expect a modest precipitation of 5 mm (0.2 in) spread over just 1 day. The climate is complemented by an average humidity of 68%, creating a warm and inviting atmosphere.

September Temperature in Rancho Cucamonga

In September in Rancho Cucamonga, the average temperature is 24°C (76°F). The maximum can reach 46°C (115°F) and the minimum can be as low as 11°C (52°F). Be prepared for a wide range of temperatures and pack accordingly for your travels.

September Weather in Rancho Cucamonga: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Rancho Cucamonga, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Rancho Cucamonga, September typically has an average temperature of 24°C (76°F), with highs reaching up to 46°C (115°F) and lows dropping to around 11°C (52°F).

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

September Precipitation in Rancho Cucamonga

In Rancho Cucamonga in September, the precipitation amount is 5 mm (0.2 in) over a duration of 1 day.

September Precipitation Trends in Rancho Cucamonga

The chart displays monthly precipitation patterns in Rancho Cucamonga, 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 Rancho Cucamonga, September typically receives around 5 mm (0.2 inches) of precipitation spread over approximately 1 days.

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

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

September Humidity in Rancho Cucamonga

In Rancho Cucamonga in September humidity is 68%. With an average temperature of 24°C (76°F), this humidity feels like a warm, steamy embrace that makes traveling both invigorating and slightly exhausting, as the air clings to your skin and encourages leisurely breaks in the shade.

September Average Humidity in Rancho Cucamonga

This chart illustrates the average monthly humidity levels in Rancho Cucamonga, 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 Rancho Cucamonga is approximately 68%, 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 Rancho Cucamonga

In Rancho Cucamonga 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 Rancho Cucamonga.

Maximum UV Index Levels in Rancho Cucamonga for September

The chart shows the monthly maximum UV Index (UVI) for Rancho Cucamonga 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 Rancho Cucamonga typically reaches 10, which falls under the very high exposure category.

Data source: Rancho Cucamonga 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 Rancho Cucamonga Compares to Other Months

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

This table compares monthly weather conditions in Rancho Cucamonga, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	12°C (54°F)	87 mm (3.4 inches)	74%	moderate
February Weather	12°C (54°F)	84 mm (3.3 inches)	79%	high
March Weather	14°C (57°F)	95 mm (3.7 inches)	75%	very high
April Weather	17°C (63°F)	35 mm (1.4 inches)	70%	very high
May Weather	18°C (66°F)	23 mm (0.9 inches)	70%	very high
June Weather	23°C (73°F)	3 mm (0.1 inches)	72%	extreme
July Weather	26°C (80°F)	1 mm (0.1 inches)	73%	extreme
August Weather	26°C (80°F)	2 mm (0.1 inches)	69%	very high
September Weather	24°C (76°F)	5 mm (0.2 inches)	68%	very high
October Weather	20°C (69°F)	15 mm (0.6 inches)	67%	high
November Weather	16°C (61°F)	35 mm (1.4 inches)	68%	moderate
December Weather	12°C (54°F)	87 mm (3.4 inches)	71%	moderate