nomadseason

September Weather in San Rafael, United States

Last updated: June 24, 2025

In September, the average temperature in San Rafael, United States hovers around 18°C (65°F). Expect a range where the minimum dips to 1°C (34°F), while maximums can soar to a warm 33°C (91°F). During this time, you'll encounter approximately 32 mm (1.3 in) of precipitation spread over about 5 days, with an average humidity of 62%. Enjoy the varied climate, and don't forget your umbrella!

September Temperature in San Rafael

In September in San Rafael, the average temperature is 18°C (65°F). Maximums can reach 33°C (91°F), while minimums can drop as low as 1°C (34°F). Be prepared for a diverse range of temperatures when you travel, ensuring you're equipped for both warm days and cooler nights.

September Weather in San Rafael: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in San Rafael, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In San Rafael, September typically has an average temperature of 18°C (65°F), with highs reaching up to 33°C (91°F) and lows dropping to around 1°C (34°F).
JanFebMarAprMayJunJulAugSepOctNovDec293342516071727064524232
Data source: Temperature data for San Rafael generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in San Rafael

In San Rafael in September, the precipitation amount is 32 mm (1.3 in) over the course of 5 days.

September Precipitation Trends in San Rafael

The chart displays monthly precipitation patterns in San Rafael, 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 Rafael, September typically receives around 32 mm (1.3 inches) of precipitation spread over approximately 5 days.
JanFebMarAprMayJunJulAugSepOctNovDec242332201612583632241421
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

September Humidity in San Rafael

In San Rafael in September, humidity is 62%. With an average temperature of 18°C (65°F), this humidity feels like a warm embrace, making outdoor activities enjoyable yet mildly sticky, perfect for leisurely strolls but a bit challenging for vigorous excursions.

September Average Humidity in San Rafael

This chart illustrates the average monthly humidity levels in San Rafael, 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 Rafael is approximately 62%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec81%83%71%61%48%36%37%46%62%74%82%82%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in San Rafael

In San Rafael in September, the maximum UV index reaches 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, you can check the Hourly UV Index in San Rafael.

Maximum UV Index Levels in San Rafael for September

The chart shows the monthly maximum UV Index (UVI) for San Rafael 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 Rafael typically reaches 11, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec579111213131211864
Data source: San Rafael 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 Rafael Compares to Other Months

Weather in San Rafael varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in San Rafael, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in San Rafael, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-2°C (29°F)24 mm (1.0 inches)81%moderate
February Weather1°C (34°F)23 mm (0.9 inches)83%high
March Weather6°C (43°F)31 mm (1.2 inches)71%very high
April Weather10°C (51°F)20 mm (0.8 inches)61%extreme
May Weather15°C (60°F)16 mm (0.6 inches)48%extreme
June Weather22°C (71°F)12 mm (0.5 inches)36%extreme
July Weather22°C (72°F)58 mm (2.3 inches)37%extreme
August Weather21°C (70°F)36 mm (1.4 inches)46%extreme
September Weather18°C (65°F)32 mm (1.3 inches)62%extreme
October Weather11°C (53°F)23 mm (0.9 inches)74%very high
November Weather6°C (42°F)14 mm (0.6 inches)82%high
December Weather0°C (32°F)21 mm (0.8 inches)82%moderate

Compare San Rafael's Climate with Cities Worldwide