September Weather in Fountain Valley, United States

Last updated: June 24, 2025

The average temperature in Fountain Valley, United States during September is a pleasant 22°C (72°F). Expect minimums around 15°C (58°F) and soaring highs of up to 38°C (102°F). With a meager 3 mm (0.1 in) of precipitation spread across 0 days, the weather is likely to be quite dry. Additionally, you can anticipate an average humidity of 68%, creating a warm and comfortable atmosphere.

September Temperature in Fountain Valley

In September, in Fountain Valley, the average temperature is 22°C (72°F). Maximums can reach 38°C (102°F), while minimums can drop as low as 15°C (58°F). This makes September a great time to visit Fountain Valley, offering warm days ideal for outdoor activities and cooler nights perfect for comfortable evenings.

September Weather in Fountain Valley: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Fountain Valley, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Fountain Valley, September typically has an average temperature of 22°C (72°F), with highs reaching up to 38°C (102°F) and lows dropping to around 15°C (58°F).
JanFebMarAprMayJunJulAugSepOctNovDec575759636467727372696357
Data source: Temperature data for Fountain Valley 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 Fountain Valley

In Fountain Valley in September, the precipitation amount is 3 mm (0.1 in) during a total of 0 days.

September Precipitation Trends in Fountain Valley

The chart displays monthly precipitation patterns in Fountain Valley, 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 Fountain Valley, September typically receives around 3 mm (0.1 inches) of precipitation spread over approximately 0 days.
JanFebMarAprMayJunJulAugSepOctNovDec6552552312432391868
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

September Humidity in Fountain Valley

In Fountain Valley in September humidity is 68%. With an average temperature of 22°C (72°F), this humidity feels like a warm embrace, slightly stifling but still manageable for traveling, creating an atmosphere that encourages leisurely outdoor activities while prompting occasional breaks for refreshment.

September Average Humidity in Fountain Valley

This chart illustrates the average monthly humidity levels in Fountain Valley, 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 Fountain Valley is approximately 68%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec74%79%75%71%70%72%73%69%68%67%68%71%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Fountain Valley

In Fountain Valley 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 Fountain Valley.

Maximum UV Index Levels in Fountain Valley for September

The chart shows the monthly maximum UV Index (UVI) for Fountain Valley 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 Fountain Valley typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec468101011111010754
Data source: Fountain Valley 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 Fountain Valley Compares to Other Months

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

This table compares monthly weather conditions in Fountain Valley, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather14°C (57°F)65 mm (2.5 inches)74%moderate
February Weather14°C (58°F)52 mm (2.0 inches)79%high
March Weather15°C (60°F)55 mm (2.2 inches)75%very high
April Weather17°C (63°F)23 mm (0.9 inches)70%very high
May Weather18°C (64°F)12 mm (0.5 inches)70%very high
June Weather20°C (68°F)4 mm (0.2 inches)72%extreme
July Weather22°C (72°F)3 mm (0.1 inches)73%extreme
August Weather23°C (73°F)2 mm (0.1 inches)69%very high
September Weather22°C (72°F)3 mm (0.1 inches)68%very high
October Weather20°C (69°F)9 mm (0.4 inches)67%high
November Weather17°C (63°F)18 mm (0.7 inches)68%moderate
December Weather14°C (58°F)68 mm (2.7 inches)71%moderate

Compare Fountain Valley's Climate with Cities Worldwide