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September Weather in San Francisco, Mexico

Last updated: August 27, 2025

In San Francisco, Mexico, the average temperature in September hovers around 26°C (79°F), offering a pleasant climate. Daily temperatures can swing from a chilly 13°C (55°F) to a scorching 41°C (106°F). Expect some precipitation, totaling about 11 mm (0.4 in) over the course of 1 day, alongside an average humidity level of 75%, adding a hint of tropical allure to the atmosphere.

September Temperature in San Francisco

In September in San Francisco, the average temperature is 26°C (79°F). Maximum temperatures can reach up to 41°C (106°F), while minimums can drop as low as 13°C (55°F). Be prepared for a hot climate with significant temperature variation, so pack accordingly for your travels!

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

The chart illustrates September temperature patterns in San Francisco, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In San Francisco, September typically has an average temperature of 26°C (79°F), with highs reaching up to 41°C (106°F) and lows dropping to around 13°C (55°F).
JanFebMarAprMayJunJulAugSepOctNovDec616163666771788179746861
Data source: Temperature data for San Francisco generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in San Francisco

In San Francisco in September, the precipitation amount is 11 mm (0.4 in) over the course of one day.

September Precipitation Trends in San Francisco

The chart displays monthly precipitation patterns in San Francisco, 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 Francisco, September typically receives around 11 mm (0.4 inches) of precipitation spread over approximately 1 days.
JanFebMarAprMayJunJulAugSepOctNovDec121014111221191512
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in San Francisco

In San Francisco in September, humidity is 75%. With an average temperature of 26°C (79°F), this humidity feels like a warm blanket wrapped around you, making traveling a sticky experience where every step requires extra effort and frequent breaks to cool off.

September Average Humidity in San Francisco

This chart illustrates the average monthly humidity levels in San Francisco, 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 Francisco is approximately 75%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec72%69%61%58%61%61%63%70%75%72%72%72%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in San Francisco

In San Francisco in September, the maximum UV index is 12, which corresponds to an extreme Exposure Category. The time to burn is just 10 minutes, underscoring the importance of sun protection. For detailed information, you can check the Hourly UV Index in San Francisco.

Maximum UV Index Levels in San Francisco for September

The chart shows the monthly maximum UV Index (UVI) for San Francisco 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 Francisco typically reaches 12, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec6810121212121212975
Data source: San Francisco 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 Francisco Compares to Other Months

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

This table compares monthly weather conditions in San Francisco, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather16°C (61°F)12 mm (0.5 inches)71%high
February Weather16°C (62°F)10 mm (0.4 inches)69%very high
March Weather17°C (64°F)14 mm (0.6 inches)61%very high
April Weather19°C (67°F)1 mm (0.0 inches)58%extreme
May Weather19°C (67°F)1 mm (0.0 inches)61%extreme
June Weather22°C (72°F)1 mm (0.0 inches)61%extreme
July Weather26°C (79°F)2 mm (0.1 inches)63%extreme
August Weather27°C (81°F)2 mm (0.1 inches)70%extreme
September Weather26°C (79°F)11 mm (0.4 inches)75%extreme
October Weather23°C (74°F)9 mm (0.4 inches)71%very high
November Weather20°C (68°F)15 mm (0.6 inches)72%high
December Weather16°C (62°F)12 mm (0.5 inches)72%moderate

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