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September Weather in San Francisco, Mexico

Last updated: August 27, 2025

In September, the average temperature in San Francisco, Mexico is a pleasant 23°C (74°F). However, temperatures can fluctuate, with minimums dipping to 15°C (59°F) and maximums soaring to 37°C (98°F). This month also sees precipitation averaging 124 mm (4.9 in) over 21 days, accompanied by a high average humidity of 84%. Prepare for a warm and humid experience!

September Temperature in San Francisco

In September in San Francisco, the average temperature is 23°C (74°F). Maximums can reach 37°C (98°F), and minimums can be as low as 15°C (59°F). This makes San Francisco an ideal destination for travelers seeking a warm climate with plenty of opportunities for 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 23°C (74°F), with highs reaching up to 37°C (98°F) and lows dropping to around 15°C (59°F).
JanFebMarAprMayJunJulAugSepOctNovDec606469747776767674706561
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 124 mm (4.9 in) recorded over 21 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 124 mm (4.9 inches) of precipitation spread over approximately 21 days.
JanFebMarAprMayJunJulAugSepOctNovDec11131921551069175124113219
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 23°C (74°F), this humidity feels like a warm blanket wrapping around you, making outdoor activities feel sticky and heavy, while the air's thickness can be quite exhausting for long periods of travel.

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.
JanFebMarAprMayJunJulAugSepOctNovDec810131413131413131197
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 Weather15°C (60°F)11 mm (0.5 inches)88%very high
February Weather18°C (65°F)13 mm (0.5 inches)86%very high
March Weather20°C (69°F)19 mm (0.7 inches)83%extreme
April Weather23°C (74°F)21 mm (0.8 inches)80%extreme
May Weather25°C (78°F)55 mm (2.2 inches)82%extreme
June Weather25°C (77°F)106 mm (4.2 inches)79%extreme
July Weather24°C (76°F)91 mm (3.6 inches)72%extreme
August Weather24°C (76°F)75 mm (3.0 inches)74%extreme
September Weather23°C (74°F)124 mm (4.9 inches)84%extreme
October Weather21°C (70°F)113 mm (4.4 inches)92%extreme
November Weather18°C (65°F)21 mm (0.8 inches)91%very high
December Weather16°C (61°F)9 mm (0.3 inches)91%high

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