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September Weather in Fontana, United States

Last updated: June 24, 2025

In Fontana, United States, the average temperature in September is a pleasant 19°C (66°F). Expect a range between a chilly 2°C (37°F) and a warm 33°C (92°F). During this month, you can anticipate 104 mm (4.1 in) of precipitation spread across 9 days, contributing to an average humidity of 79%.

September Temperature in Fontana

In September in Fontana, the average temperature is 19°C (66°F), with maximums reaching up to 33°C (92°F) and minimums dipping as low as 2°C (37°F). It's essential to pack layers and be prepared for both warm days and cool evenings while traveling during this time.

September Weather in Fontana: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Fontana, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Fontana, September typically has an average temperature of 19°C (66°F), with highs reaching up to 33°C (92°F) and lows dropping to around 2°C (37°F).
JanFebMarAprMayJunJulAugSepOctNovDec232537465970757266523731
Data source: Temperature data for Fontana 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 Fontana

In Fontana in September, the precipitation amount is 104 mm (4.1 in) over the course of 9 days.

September Precipitation Trends in Fontana

The chart displays monthly precipitation patterns in Fontana, 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 Fontana, September typically receives around 104 mm (4.1 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec61586611015411584911041194952
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Fontana

In Fontana in September humidity is 79%. With an average temperature of 19°C (66°F), this humidity feels like a warm embrace, making it feel much warmer than the actual temperature and creating a heavy, sticky atmosphere that can be a bit uncomfortable for traveling.

September Average Humidity in Fontana

This chart illustrates the average monthly humidity levels in Fontana, 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 Fontana is approximately 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%85%85%85%78%80%78%76%79%83%88%82%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Fontana

In Fontana in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Fontana.

Maximum UV Index Levels in Fontana for September

The chart shows the monthly maximum UV Index (UVI) for Fontana 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 Fontana typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34689101098532
Data source: Fontana 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 Fontana Compares to Other Months

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

This table compares monthly weather conditions in Fontana, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-5°C (23°F)61 mm (2.4 inches)85%moderate
February Weather-4°C (25°F)58 mm (2.3 inches)85%moderate
March Weather3°C (37°F)66 mm (2.6 inches)85%high
April Weather8°C (47°F)110 mm (4.3 inches)85%very high
May Weather15°C (60°F)154 mm (6.0 inches)78%very high
June Weather21°C (71°F)115 mm (4.5 inches)80%very high
July Weather24°C (75°F)84 mm (3.3 inches)78%very high
August Weather22°C (72°F)91 mm (3.6 inches)76%very high
September Weather19°C (66°F)104 mm (4.1 inches)79%very high
October Weather11°C (53°F)119 mm (4.7 inches)83%moderate
November Weather3°C (37°F)49 mm (1.9 inches)88%moderate
December Weather-1°C (31°F)52 mm (2.1 inches)81%low

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