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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 27°C (82°F), creating a warm and inviting atmosphere. Expect minimums as low as 22°C (72°F) and maximums reaching up to 35°C (95°F). However, be prepared for some rain, as the area receives about 148 mm (5.8 in) of precipitation over 22 days. With an average humidity level of 82%, it's the perfect setting for enjoying both the tropical warmth and occasional refreshing showers.

September Temperature in San Francisco

In September, in San Francisco, the average temperature is 27°C (82°F). The maximum can reach 35°C (95°F) and the minimum can be as low as 22°C (72°F). This warm and pleasant climate makes San Francisco an ideal destination for travelers seeking both relaxation and adventure.

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 27°C (82°F), with highs reaching up to 35°C (95°F) and lows dropping to around 22°C (72°F).
JanFebMarAprMayJunJulAugSepOctNovDec737677808282828281807674
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 148 mm (5.8 in) over the course of 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 148 mm (5.8 inches) of precipitation spread over approximately 22 days.
JanFebMarAprMayJunJulAugSepOctNovDec3919153989164871101481746735
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 82%. With an average temperature of 27°C (82°F), this humidity feels like stepping into a warm, thick blanket, making outdoor activities quite uncomfortable and travel feel a bit sluggish.

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 82%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec81%78%71%70%68%69%74%81%82%83%84%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 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.
JanFebMarAprMayJunJulAugSepOctNovDec810121313131212121187
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 Weather23°C (73°F)38 mm (1.5 inches)81%very high
February Weather24°C (76°F)19 mm (0.8 inches)78%very high
March Weather25°C (77°F)15 mm (0.6 inches)71%extreme
April Weather27°C (81°F)38 mm (1.5 inches)70%extreme
May Weather28°C (82°F)89 mm (3.5 inches)68%extreme
June Weather28°C (82°F)164 mm (6.5 inches)69%extreme
July Weather28°C (83°F)87 mm (3.4 inches)74%extreme
August Weather28°C (83°F)110 mm (4.3 inches)81%extreme
September Weather27°C (82°F)148 mm (5.8 inches)82%extreme
October Weather26°C (80°F)174 mm (6.9 inches)83%extreme
November Weather24°C (76°F)67 mm (2.6 inches)84%very high
December Weather23°C (74°F)35 mm (1.4 inches)86%high

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