September Weather in San Dimas, United States

Last updated: June 24, 2025

In September, the average temperature in San Dimas, United States is a pleasant 23°C (74°F). During this month, you can expect the temperature to range from a minimum of 12°C (53°F) to a maximum of 44°C (111°F). With an average humidity of 68%, the weather stays fairly comfortable, and you can enjoy a minimal precipitation amount of just 3 mm (0.1 in) across 0 days.

September Temperature in San Dimas

In September in San Dimas, the average temperature is 23°C (74°F). The maximum can reach 44°C (111°F), and the minimum can be as low as 12°C (53°F). It's a great time for travelers to prepare for warm days and cooler nights, making it ideal for both outdoor adventures and cozy evenings.

September Weather in San Dimas: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in San Dimas, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In San Dimas, September typically has an average temperature of 23°C (74°F), with highs reaching up to 44°C (111°F) and lows dropping to around 12°C (53°F).

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

September Precipitation in San Dimas

In San Dimas in September, the precipitation amount is 3 mm (0.1 in) during a total of 0 days.

September Precipitation Trends in San Dimas

The chart displays monthly precipitation patterns in San Dimas, 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 San Dimas, September typically receives around 3 mm (0.1 inches) of precipitation spread over approximately 0 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 San Dimas

In San Dimas in September, humidity is 68%. With an average temperature of 23°C (74°F), this humidity feels like a warm embrace, making traveling quite uncomfortable if you're not prepared. The air is thick and muggy, leaving you yearning for a cool breeze and frequent breaks in the shade.

September Average Humidity in San Dimas

This chart illustrates the average monthly humidity levels in San Dimas, 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 San Dimas 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 San Dimas

In San Dimas 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 San Dimas.

Maximum UV Index Levels in San Dimas for September

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

Data source: San Dimas 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 San Dimas Compares to Other Months

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

This table compares monthly weather conditions in San Dimas, 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)	80 mm (3.1 inches)	74%	moderate
February Weather	12°C (55°F)	70 mm (2.8 inches)	79%	high
March Weather	14°C (57°F)	76 mm (3.0 inches)	75%	very high
April Weather	16°C (62°F)	27 mm (1.1 inches)	70%	very high
May Weather	18°C (64°F)	17 mm (0.7 inches)	70%	very high
June Weather	21°C (70°F)	1 mm (0.0 inches)	72%	extreme
July Weather	24°C (76°F)	1 mm (0.1 inches)	73%	extreme
August Weather	25°C (77°F)	2 mm (0.1 inches)	69%	very high
September Weather	23°C (74°F)	3 mm (0.1 inches)	68%	very high
October Weather	20°C (68°F)	12 mm (0.5 inches)	67%	high
November Weather	16°C (61°F)	26 mm (1.0 inches)	68%	moderate
December Weather	12°C (54°F)	79 mm (3.1 inches)	71%	moderate