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September Weather in Santa Rosa, United States

Last updated: June 24, 2025

In Santa Rosa, United States, the average temperature in September reaches a warm 30°C (86°F). However, temperatures can vary significantly, with a minimum of 13°C (56°F) and a scorching maximum of 44°C (111°F). During this month, expect a total precipitation of 15 mm (0.6 in) over about 2 days, with an average humidity level of 64%.

September Temperature in Santa Rosa

In September in Santa Rosa, the average temperature is 30°C (86°F). Maximums can reach 44°C (111°F), and minimums can be as low as 13°C (56°F). It's a great time to visit if you enjoy warm weather but be prepared for the potential heat and varying temperatures.

September Weather in Santa Rosa: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Santa Rosa, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Santa Rosa, September typically has an average temperature of 30°C (86°F), with highs reaching up to 44°C (111°F) and lows dropping to around 13°C (56°F).
JanFebMarAprMayJunJulAugSepOctNovDec555764737989919186756655
Data source: Temperature data for Santa Rosa 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 Santa Rosa

In Santa Rosa in September, the precipitation amount is 15 mm (0.6 in) over the course of 2 days.

September Precipitation Trends in Santa Rosa

The chart displays monthly precipitation patterns in Santa Rosa, 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 Santa Rosa, September typically receives around 15 mm (0.6 inches) of precipitation spread over approximately 2 days.
JanFebMarAprMayJunJulAugSepOctNovDec1818132173424157818
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Santa Rosa

In Santa Rosa in September humidity is 64%. With an average temperature of 30°C (86°F), this humidity feels like a warm, sticky embrace that can make outdoor activities uncomfortable and somewhat draining for travelers.

September Average Humidity in Santa Rosa

This chart illustrates the average monthly humidity levels in Santa Rosa, 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 Santa Rosa is approximately 64%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec76%79%67%55%40%33%34%48%64%67%77%82%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Santa Rosa

In Santa Rosa in September, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in Santa Rosa.

Maximum UV Index Levels in Santa Rosa for September

The chart shows the monthly maximum UV Index (UVI) for Santa Rosa 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 Santa Rosa typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec579111212121110864
Data source: Santa Rosa 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 Santa Rosa Compares to Other Months

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

This table compares monthly weather conditions in Santa Rosa, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather13°C (55°F)18 mm (0.7 inches)76%moderate
February Weather14°C (58°F)18 mm (0.7 inches)79%high
March Weather18°C (64°F)13 mm (0.5 inches)67%very high
April Weather23°C (73°F)2 mm (0.1 inches)55%extreme
May Weather26°C (79°F)1 mm (0.0 inches)40%extreme
June Weather32°C (89°F)7 mm (0.3 inches)33%extreme
July Weather33°C (91°F)34 mm (1.3 inches)34%extreme
August Weather33°C (91°F)24 mm (0.9 inches)48%extreme
September Weather30°C (86°F)15 mm (0.6 inches)64%very high
October Weather24°C (76°F)7 mm (0.3 inches)67%very high
November Weather19°C (66°F)8 mm (0.3 inches)77%high
December Weather13°C (56°F)18 mm (0.7 inches)82%moderate

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