September Weather in Los Altos Hills, United States

Last updated: June 24, 2025

In September, the average temperature in Los Altos Hills, United States is a pleasant 18°C (66°F), making it an ideal time to explore the area. Expect temperatures to range from a cool 10°C (50°F) to a warm 39°C (103°F). With only 2 mm (0.1 in) of precipitation over 0 days, you'll likely enjoy clear skies. The average humidity sits at a comfortable 55%, ensuring a delightful atmosphere for any outdoor activities.

September Temperature in Los Altos Hills

In September in Los Altos Hills, the average temperature is 18°C (66°F), with maximums reaching up to 39°C (103°F) and minimums dropping as low as 10°C (50°F). Be prepared for warm days and cooler nights when planning your travel to Los Altos Hills.

September Weather in Los Altos Hills: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Los Altos Hills, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Los Altos Hills, September typically has an average temperature of 18°C (66°F), with highs reaching up to 39°C (103°F) and lows dropping to around 10°C (50°F).

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

September Precipitation in Los Altos Hills

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

September Precipitation Trends in Los Altos Hills

The chart displays monthly precipitation patterns in Los Altos Hills, 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 Los Altos Hills, 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 Los Altos Hills

In Los Altos Hills in September humidity is 55%. With an average temperature of 18°C (66°F), this humidity feels like a refreshing embrace, making for comfortable travels as long as you stay hydrated and enjoy the mild weather.

September Average Humidity in Los Altos Hills

This chart illustrates the average monthly humidity levels in Los Altos Hills, 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 Los Altos Hills is approximately 55%, 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 Los Altos Hills

In Los Altos Hills in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Los Altos Hills.

Maximum UV Index Levels in Los Altos Hills for September

The chart shows the monthly maximum UV Index (UVI) for Los Altos Hills 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 Los Altos Hills typically reaches 9, which falls under the very high exposure category.

Data source: Los Altos Hills 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 Los Altos Hills Compares to Other Months

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

This table compares monthly weather conditions in Los Altos Hills, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	11°C (52°F)	105 mm (4.1 inches)	82%	moderate
February Weather	11°C (53°F)	100 mm (3.9 inches)	84%	moderate
March Weather	12°C (54°F)	86 mm (3.4 inches)	82%	very high
April Weather	13°C (57°F)	33 mm (1.3 inches)	78%	very high
May Weather	15°C (59°F)	24 mm (0.9 inches)	71%	very high
June Weather	17°C (63°F)	2 mm (0.1 inches)	64%	extreme
July Weather	17°C (63°F)	0 mm (0.0 inches)	58%	extreme
August Weather	18°C (65°F)	0 mm (0.0 inches)	54%	very high
September Weather	18°C (66°F)	2 mm (0.1 inches)	55%	very high
October Weather	17°C (63°F)	24 mm (0.9 inches)	62%	high
November Weather	13°C (56°F)	47 mm (1.9 inches)	78%	moderate
December Weather	11°C (52°F)	88 mm (3.5 inches)	80%	moderate