September Weather in Simi Valley, United States

Last updated: June 24, 2025

In September, the average temperature in Simi Valley, United States is a pleasant 22°C (73°F), with the mercury occasionally dipping to a minimum of 11°C (52°F) and soaring to a maximum of 43°C (110°F). This month sees minimal precipitation of only 2 mm (0.1 in) over 0 days, contributing to an average humidity of 48%. Enjoy the balmy weather!

September Temperature in Simi Valley

In September in Simi Valley, the average temperature is 22°C (73°F). The maximum can reach 43°C (110°F), while the minimum can dip as low as 11°C (52°F). Be prepared for a range of temperatures and pack accordingly for your trip!

September Weather in Simi Valley: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Simi Valley, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Simi Valley, September typically has an average temperature of 22°C (73°F), with highs reaching up to 43°C (110°F) and lows dropping to around 11°C (52°F).

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

September Precipitation in Simi Valley

In Simi Valley in September, the precipitation amount is 2 mm (0.1 in) during a span of 0 days.

September Precipitation Trends in Simi Valley

The chart displays monthly precipitation patterns in Simi Valley, 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 Simi Valley, September typically receives around 2 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 Simi Valley

In Simi Valley in September, humidity is 48%. With an average temperature of 22°C (73°F), this humidity feels like a comfortable environment for traveling, allowing you to explore without the oppressive stickiness that higher humidity can bring.

September Average Humidity in Simi Valley

This chart illustrates the average monthly humidity levels in Simi Valley, 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 Simi Valley is approximately 48%, 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 Simi Valley

In Simi Valley 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 Simi Valley.

Maximum UV Index Levels in Simi Valley for September

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

Data source: Simi Valley 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 Simi Valley Compares to Other Months

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

This table compares monthly weather conditions in Simi Valley, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	13°C (55°F)	79 mm (3.1 inches)	78%	moderate
February Weather	13°C (55°F)	63 mm (2.5 inches)	82%	high
March Weather	14°C (57°F)	80 mm (3.2 inches)	75%	very high
April Weather	17°C (62°F)	20 mm (0.8 inches)	68%	very high
May Weather	17°C (64°F)	15 mm (0.6 inches)	57%	extreme
June Weather	20°C (69°F)	2 mm (0.1 inches)	52%	extreme
July Weather	23°C (74°F)	1 mm (0.0 inches)	46%	extreme
August Weather	24°C (75°F)	1 mm (0.0 inches)	39%	extreme
September Weather	22°C (73°F)	2 mm (0.1 inches)	48%	very high
October Weather	20°C (68°F)	10 mm (0.4 inches)	59%	high
November Weather	16°C (62°F)	19 mm (0.7 inches)	72%	moderate
December Weather	12°C (55°F)	86 mm (3.4 inches)	76%	moderate