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September Weather in San Francisco, Mexico

Last updated: August 27, 2025

In September, the average temperature in San Francisco, Mexico hovers around 25°C (77°F). Expect a comfortable climate, with minimums dipping to 16°C (61°F) and maximums peaking at 34°C (93°F). However, be prepared for some damp days, as the area experiences an average precipitation of 212 mm (8.4 in) over 22 days, accompanied by a high average humidity of 84%.

September Temperature in San Francisco

In September in San Francisco, the average temperature is 25°C (77°F), with maximums reaching up to 34°C (93°F) and minimums dropping as low as 16°C (61°F). This pleasant weather makes it an ideal time for travelers to explore and enjoy outdoor activities in San Francisco.

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 25°C (77°F), with highs reaching up to 34°C (93°F) and lows dropping to around 16°C (61°F).
JanFebMarAprMayJunJulAugSepOctNovDec636669747878777777736864
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 total precipitation amount is 212 mm (8.4 in) spread over 22 days.

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 212 mm (8.4 inches) of precipitation spread over approximately 22 days.
JanFebMarAprMayJunJulAugSepOctNovDec927911211718521114119121228712762
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 84%. With an average temperature of 25°C (77°F), this humidity feels like a warm, enveloping blanket that clings to your skin, making outdoor activities challenging and prompting travelers to seek shade and stay hydrated.

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 84%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec89%86%83%80%82%79%72%74%84%92%91%91%
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 reaches 13, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's crucial to take protective measures. 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 13, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec811121313131313131197
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 Weather17°C (63°F)92 mm (3.6 inches)88%very high
February Weather19°C (66°F)79 mm (3.1 inches)86%extreme
March Weather21°C (70°F)112 mm (4.4 inches)83%extreme
April Weather23°C (74°F)117 mm (4.6 inches)80%extreme
May Weather25°C (78°F)185 mm (7.3 inches)82%extreme
June Weather25°C (78°F)210 mm (8.3 inches)79%extreme
July Weather25°C (77°F)141 mm (5.5 inches)72%extreme
August Weather25°C (78°F)191 mm (7.5 inches)74%extreme
September Weather25°C (77°F)212 mm (8.4 inches)84%extreme
October Weather23°C (74°F)287 mm (11.3 inches)92%extreme
November Weather20°C (68°F)127 mm (5.0 inches)91%very high
December Weather18°C (64°F)62 mm (2.4 inches)91%high

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