nomadseason

September Weather in Los Altos, United States

Last updated: June 24, 2025

In Los Altos, United States, the average temperature in September hovers around 20°C (69°F). Visitors can expect a range, with temperatures dipping as low as 8°C (47°F) and peaking at a sizzling 43°C (110°F). Rainfall is minimal, averaging just 2 mm (0.1 in) across 0 days, while humidity remains reasonably comfortable at 55%. Enjoy the pleasant weather!

September Temperature in Los Altos

In September in Los Altos, the average temperature is 20°C (69°F). The maximum can reach 43°C (110°F) and the minimum can be as low as 8°C (47°F). It's important to pack for both warmth and heat when traveling during this month.

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

The chart illustrates September temperature patterns in Los Altos, 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, September typically has an average temperature of 20°C (69°F), with highs reaching up to 43°C (110°F) and lows dropping to around 8°C (47°F).
JanFebMarAprMayJunJulAugSepOctNovDec505254576066687068645650
Data source: Temperature data for Los Altos generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Los Altos

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

September Precipitation Trends in Los Altos

The chart displays monthly precipitation patterns in Los Altos, 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, September typically receives around 2 mm (0.1 inches) of precipitation spread over approximately 0 days.
JanFebMarAprMayJunJulAugSepOctNovDec98958731241002224081
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

September Humidity in Los Altos

In Los Altos in September humidity is 55%. With an average temperature of 20°C (69°F), this humidity feels like a refreshing embrace, making it ideal for exploring the local sights while still requiring a light layer to stay comfortable.

September Average Humidity in Los Altos

This chart illustrates the average monthly humidity levels in Los Altos, 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 is approximately 55%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%84%82%78%71%64%59%54%55%62%78%80%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Los Altos

In Los Altos 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.

Maximum UV Index Levels in Los Altos for September

The chart shows the monthly maximum UV Index (UVI) for Los Altos 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 typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3589101111109753
Data source: Los Altos 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 Compares to Other Months

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

This table compares monthly weather conditions in Los Altos, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather10°C (51°F)98 mm (3.9 inches)82%moderate
February Weather11°C (52°F)95 mm (3.8 inches)84%moderate
March Weather12°C (54°F)87 mm (3.4 inches)82%very high
April Weather14°C (57°F)30 mm (1.2 inches)78%very high
May Weather16°C (61°F)23 mm (0.9 inches)71%very high
June Weather19°C (66°F)1 mm (0.0 inches)64%extreme
July Weather20°C (69°F)0 mm (0.0 inches)58%extreme
August Weather21°C (70°F)0 mm (0.0 inches)54%very high
September Weather20°C (69°F)2 mm (0.1 inches)55%very high
October Weather18°C (64°F)22 mm (0.9 inches)62%high
November Weather13°C (56°F)40 mm (1.6 inches)78%moderate
December Weather10°C (51°F)81 mm (3.2 inches)80%moderate

Compare Los Altos's Climate with Cities Worldwide