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September Weather in San Francisco, Argentina

Last updated: August 22, 2025

In September, the average temperature in San Francisco, Argentina is a pleasant 17°C (63°F). However, temperatures can vary significantly, dropping to a chilly 2°C (36°F) at night or soaring to a scorching 38°C (100°F) during the day. Expect 37 mm (1.5 in) of precipitation over about 5 days, with an average humidity level of 59%, adding a touch of moisture to the air.

September Temperature in San Francisco

In September in San Francisco, the average temperature is 17°C (63°F). Maximum temperatures can reach 38°C (100°F), while minimums can drop to as low as 2°C (36°F). This makes San Francisco a great destination for travelers seeking a diverse climate, so be sure to pack accordingly!

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 17°C (63°F), with highs reaching up to 38°C (100°F) and lows dropping to around 2°C (36°F).
JanFebMarAprMayJunJulAugSepOctNovDec777571675954535762677376
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 37 mm (1.5 in) spread over a period of 5 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 37 mm (1.5 inches) of precipitation spread over approximately 5 days.
JanFebMarAprMayJunJulAugSepOctNovDec10570901206119191437898495
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 59%. With an average temperature of 17°C (63°F), this humidity feels like a refreshing embrace, making it pleasant for traveling as long as you're prepared for occasional mugginess.

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 59%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec51%57%65%76%83%78%58%54%59%50%53%57%
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 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. 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 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec141312864569111414
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 Weather25°C (78°F)105 mm (4.1 inches)51%extreme
February Weather24°C (75°F)70 mm (2.8 inches)57%extreme
March Weather22°C (72°F)90 mm (3.5 inches)65%extreme
April Weather19°C (67°F)120 mm (4.7 inches)76%very high
May Weather15°C (59°F)61 mm (2.4 inches)83%high
June Weather12°C (54°F)19 mm (0.7 inches)78%moderate
July Weather11°C (53°F)19 mm (0.8 inches)58%moderate
August Weather14°C (57°F)14 mm (0.5 inches)54%high
September Weather17°C (63°F)37 mm (1.5 inches)59%very high
October Weather19°C (67°F)89 mm (3.5 inches)50%extreme
November Weather23°C (73°F)84 mm (3.3 inches)53%extreme
December Weather24°C (76°F)95 mm (3.7 inches)57%extreme

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