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September Weather in San Francisco, Peru

Last updated: August 27, 2025

In September, the average temperature in San Francisco, Peru is a pleasant 18°C (64°F), with a comfortable humidity of 53%. Expect lows of 14°C (57°F) and highs reaching up to 23°C (74°F). With a mere 2 mm (0.1 in) of precipitation over 0 days, you can enjoy clear skies and delightful weather!

September Temperature in San Francisco

In September in San Francisco, the average temperature is 18°C (64°F). The maximum can reach 23°C (74°F), and the minimum can be as low as 14°C (57°F). This mild and pleasant climate makes it an ideal time for traveling and enjoying outdoor activities 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 18°C (64°F), with highs reaching up to 23°C (74°F) and lows dropping to around 14°C (57°F).
JanFebMarAprMayJunJulAugSepOctNovDec686969686664646464646567
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 2 mm (0.1 in) during a span of 0 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 2 mm (0.1 inches) of precipitation spread over approximately 0 days.
JanFebMarAprMayJunJulAugSepOctNovDec73845820421125513
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 53%. With an average temperature of 18°C (64°F), this humidity feels like a comfortable embrace, allowing for enjoyable outdoor exploration and leisurely strolls without overwhelming heat or discomfort.

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 53%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec89%89%90%89%83%69%56%51%53%68%82%87%
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.
JanFebMarAprMayJunJulAugSepOctNovDec151615141110111214151615
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 Weather20°C (69°F)73 mm (2.9 inches)89%extreme
February Weather21°C (69°F)84 mm (3.3 inches)89%extreme
March Weather21°C (70°F)58 mm (2.3 inches)90%extreme
April Weather20°C (68°F)20 mm (0.8 inches)89%extreme
May Weather19°C (66°F)4 mm (0.2 inches)83%extreme
June Weather18°C (65°F)1 mm (0.1 inches)69%very high
July Weather18°C (64°F)1 mm (0.0 inches)56%extreme
August Weather18°C (64°F)0 mm (0.0 inches)50%extreme
September Weather18°C (64°F)2 mm (0.1 inches)53%extreme
October Weather18°C (65°F)5 mm (0.2 inches)68%extreme
November Weather19°C (66°F)5 mm (0.2 inches)81%extreme
December Weather19°C (67°F)13 mm (0.5 inches)87%extreme

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