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September Weather in San Francisco, Mexico

Last updated: August 26, 2025

In September, the average temperature in San Francisco, Mexico is a warm 28°C (83°F), with lows of 25°C (78°F) and highs reaching 31°C (88°F). Expect 266 mm (10.5 in) of rain over 23 days, contributing to a high average humidity of 78%. Stay prepared for the tropical weather!

September Temperature in San Francisco

In September in San Francisco, the average temperature is 28°C (83°F), with maximums reaching 31°C (88°F) and minimums as low as 25°C (78°F). This pleasant weather makes it an ideal time for travel and outdoor activities.

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 28°C (83°F), with highs reaching up to 31°C (88°F) and lows dropping to around 25°C (78°F).
JanFebMarAprMayJunJulAugSepOctNovDec747474757881848483838177
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 266 mm (10.5 in) spread over 23 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 266 mm (10.5 inches) of precipitation spread over approximately 23 days.
JanFebMarAprMayJunJulAugSepOctNovDec2322003671302252661971915
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 78%. With an average temperature of 28°C (83°F), this humidity feels like a heavy blanket enveloping you, making outdoor activities perspire more quickly and requiring frequent breaks in the shade for comfort.

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 78%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec71%69%67%66%69%78%79%78%78%75%74%74%
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.
JanFebMarAprMayJunJulAugSepOctNovDec810121313131213121197
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 Weather24°C (75°F)23 mm (0.9 inches)71%very high
February Weather23°C (74°F)22 mm (0.9 inches)69%very high
March Weather23°C (74°F)0 mm (0.0 inches)67%extreme
April Weather24°C (76°F)0 mm (0.0 inches)66%extreme
May Weather25°C (78°F)3 mm (0.1 inches)69%extreme
June Weather27°C (81°F)67 mm (2.6 inches)78%extreme
July Weather29°C (84°F)130 mm (5.1 inches)79%extreme
August Weather29°C (84°F)225 mm (8.9 inches)78%extreme
September Weather28°C (83°F)266 mm (10.5 inches)78%extreme
October Weather28°C (83°F)197 mm (7.7 inches)75%extreme
November Weather27°C (81°F)19 mm (0.8 inches)74%very high
December Weather25°C (77°F)15 mm (0.6 inches)74%high

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