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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 21°C (70°F), providing a pleasant climate for outdoor activities. Expect minimums of 14°C (58°F) and maximums reaching 28°C (83°F). However, be prepared for some rain, as 197 mm (7.8 in) of precipitation is distributed over 24 days. With an average humidity of 77%, it’s a great time to enjoy the lush landscapes that thrive in this environment.

September Temperature in San Francisco

In September in San Francisco, the average temperature is 21°C (70°F). The maximum can reach 28°C (83°F) and the minimum can be as low as 14°C (58°F). This mild and pleasant climate makes it an ideal time for outdoor activities and exploration 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 21°C (70°F), with highs reaching up to 28°C (83°F) and lows dropping to around 14°C (58°F).
JanFebMarAprMayJunJulAugSepOctNovDec616365707270697070686562
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 197 mm (7.8 in) over the course of 24 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 197 mm (7.8 inches) of precipitation spread over approximately 24 days.
JanFebMarAprMayJunJulAugSepOctNovDec8153465513229710415919720511363
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 77%. With an average temperature of 21°C (70°F), this humidity feels like a warm, slightly sticky embrace, making travel invigorating yet slightly uncomfortable as you navigate the vibrant streets and outdoor attractions.

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 77%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%73%59%53%54%55%61%71%77%78%82%86%
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 14, which corresponds to an extreme Exposure Category. The time to burn is just 10 minutes, so it's crucial to take precautions. For the detailed hourly UV index in San Francisco, you can check here.

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 14, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec10121414141414141413109
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 (62°F)81 mm (3.2 inches)84%very high
February Weather17°C (64°F)53 mm (2.1 inches)73%extreme
March Weather18°C (65°F)46 mm (1.8 inches)59%extreme
April Weather21°C (70°F)55 mm (2.2 inches)52%extreme
May Weather22°C (72°F)132 mm (5.2 inches)53%extreme
June Weather21°C (70°F)297 mm (11.7 inches)55%extreme
July Weather20°C (69°F)104 mm (4.1 inches)61%extreme
August Weather21°C (70°F)159 mm (6.2 inches)71%extreme
September Weather21°C (70°F)197 mm (7.8 inches)77%extreme
October Weather20°C (69°F)205 mm (8.1 inches)78%extreme
November Weather18°C (65°F)113 mm (4.4 inches)82%very high
December Weather17°C (63°F)63 mm (2.5 inches)86%very high

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