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September Weather in San Francisco, Mexico

Last updated: August 26, 2025

In San Francisco, Mexico, the average temperature for September is a comfortable 20°C (68°F), with minimums dipping to 14°C (58°F) and maximums climbing to 30°C (85°F). However, be prepared for a fair share of rain, with 278 mm (10.9 in) of precipitation expected across 26 days. Additionally, the average humidity levels can reach a humid 83%, making it essential to stay hydrated during your time here!

September Temperature in San Francisco

In September in San Francisco, the average temperature is 20°C (68°F), with maximums reaching 30°C (85°F) and minimums dropping as low as 14°C (58°F). This pleasant climate makes it an ideal time for travelers to explore and enjoy the outdoor attractions of 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 20°C (68°F), with highs reaching up to 30°C (85°F) and lows dropping to around 14°C (58°F).
JanFebMarAprMayJunJulAugSepOctNovDec616367697170686868676461
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 278 mm (10.9 in) over a period of 26 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 278 mm (10.9 inches) of precipitation spread over approximately 26 days.
JanFebMarAprMayJunJulAugSepOctNovDec9147343207280313278139347
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 83%. With an average temperature of 20°C (68°F), this humidity feels like a warm, heavy blanket enveloping you, making it feel much warmer than it is. Traveling in such conditions can be quite taxing, as the air feels thick, often leading to a sense of exhaustion and requiring frequent breaks to seek shade or hydration.

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 83%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec70%65%59%60%67%80%81%83%83%80%77%76%
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.
JanFebMarAprMayJunJulAugSepOctNovDec911141414141313141298
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)9 mm (0.3 inches)70%very high
February Weather17°C (64°F)14 mm (0.6 inches)65%extreme
March Weather19°C (67°F)7 mm (0.3 inches)59%extreme
April Weather21°C (69°F)3 mm (0.1 inches)60%extreme
May Weather22°C (71°F)43 mm (1.7 inches)67%extreme
June Weather21°C (70°F)207 mm (8.1 inches)80%extreme
July Weather20°C (68°F)280 mm (11.0 inches)81%extreme
August Weather20°C (68°F)313 mm (12.3 inches)83%extreme
September Weather20°C (68°F)278 mm (10.9 inches)83%extreme
October Weather19°C (67°F)139 mm (5.5 inches)80%extreme
November Weather18°C (65°F)34 mm (1.3 inches)77%very high
December Weather16°C (62°F)7 mm (0.3 inches)76%very high

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