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September Weather in San Ramon, United States

Last updated: June 24, 2025

In San Ramon, United States, the average temperature in September hovers around 20°C (68°F), with a minimum of 6°C (44°F) and a maximum reaching up to 42°C (107°F). Expect minimal precipitation of just 2 mm (0.1 in) across 0 days, making for a typically dry month. The air remains comfortably cool with an average humidity of 55%.

September Temperature in San Ramon

In September in San Ramon, the average temperature is 20°C (68°F). Maximums can reach 42°C (107°F), while minimums can drop as low as 6°C (44°F). It's advisable to pack layers and stay hydrated while exploring the varied climate.

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

The chart illustrates September temperature patterns in San Ramon, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In San Ramon, September typically has an average temperature of 20°C (68°F), with highs reaching up to 42°C (107°F) and lows dropping to around 6°C (44°F).
JanFebMarAprMayJunJulAugSepOctNovDec505254576166686867635550
Data source: Temperature data for San Ramon 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 Ramon

In San Ramon in September, the precipitation amount is 2 mm (0.1 in) during a span of 0 days.

September Precipitation Trends in San Ramon

The chart displays monthly precipitation patterns in San Ramon, 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 Ramon, September typically receives around 2 mm (0.1 inches) of precipitation spread over approximately 0 days.
JanFebMarAprMayJunJulAugSepOctNovDec94897730172002223876
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in San Ramon

In San Ramon in September humidity is 55%. With an average temperature of 20°C (68°F), this humidity feels like a warm embrace, making it comfortable for traveling but slightly sticky, encouraging leisurely strolls and relaxed outdoor activities.

September Average Humidity in San Ramon

This chart illustrates the average monthly humidity levels in San Ramon, 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 Ramon is approximately 55%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%84%82%78%71%64%59%54%55%62%78%80%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in San Ramon

In San Ramon 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 Ramon.

Maximum UV Index Levels in San Ramon for September

The chart shows the monthly maximum UV Index (UVI) for San Ramon 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 Ramon typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3589101111109753
Data source: San Ramon 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 Ramon Compares to Other Months

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

This table compares monthly weather conditions in San Ramon, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather10°C (50°F)94 mm (3.7 inches)82%moderate
February Weather11°C (52°F)89 mm (3.5 inches)84%moderate
March Weather12°C (54°F)77 mm (3.0 inches)82%very high
April Weather14°C (58°F)30 mm (1.2 inches)78%very high
May Weather16°C (61°F)17 mm (0.7 inches)71%very high
June Weather19°C (66°F)2 mm (0.1 inches)64%extreme
July Weather20°C (68°F)0 mm (0.0 inches)58%extreme
August Weather20°C (69°F)0 mm (0.0 inches)54%very high
September Weather20°C (68°F)2 mm (0.1 inches)55%very high
October Weather17°C (63°F)22 mm (0.9 inches)62%high
November Weather13°C (55°F)38 mm (1.5 inches)78%moderate
December Weather10°C (50°F)76 mm (3.0 inches)80%moderate

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