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September Weather in Fairfield, United States

Last updated: June 24, 2025

In Fairfield, United States, the average temperature in September is a warm 27°C (81°F), with a minimum dipping to 11°C (51°F) and soaring to a maximum of 39°C (103°F). Visitors can expect 100 mm (4.0 in) of precipitation over about 10 days, accompanied by an average humidity of 69%.

September Temperature in Fairfield

In September in Fairfield, the average temperature is 27°C (81°F). Maximums can reach 39°C (103°F), while minimums can drop to as low as 11°C (51°F). Be sure to pack lightweight clothes for the daytime and a warmer layer for the cooler evenings if you're traveling during this time.

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

The chart illustrates September temperature patterns in Fairfield, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Fairfield, September typically has an average temperature of 27°C (81°F), with highs reaching up to 39°C (103°F) and lows dropping to around 11°C (51°F).
JanFebMarAprMayJunJulAugSepOctNovDec505262667582868681705954
Data source: Temperature data for Fairfield 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 Fairfield

In Fairfield in September, the precipitation amount is 100 mm (4.0 in) over the course of 10 days.

September Precipitation Trends in Fairfield

The chart displays monthly precipitation patterns in Fairfield, 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 Fairfield, September typically receives around 100 mm (4.0 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec841131051171718266861001176992
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Fairfield

In Fairfield in September, humidity is 69%. With an average temperature of 27°C (81°F), this humidity feels like a warm blanket wrapped around you, making it essential to stay hydrated and take frequent breaks during your travels.

September Average Humidity in Fairfield

This chart illustrates the average monthly humidity levels in Fairfield, 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 Fairfield is approximately 69%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec80%80%78%79%81%77%71%67%69%73%82%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Fairfield

In Fairfield 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 Fairfield.

Maximum UV Index Levels in Fairfield for September

The chart shows the monthly maximum UV Index (UVI) for Fairfield 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 Fairfield typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec478111111121110864
Data source: Fairfield 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 Fairfield Compares to Other Months

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

This table compares monthly weather conditions in Fairfield, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather10°C (50°F)84 mm (3.3 inches)79%moderate
February Weather11°C (52°F)113 mm (4.5 inches)80%high
March Weather17°C (62°F)105 mm (4.1 inches)78%very high
April Weather19°C (67°F)117 mm (4.6 inches)79%extreme
May Weather24°C (75°F)171 mm (6.7 inches)81%extreme
June Weather28°C (82°F)82 mm (3.2 inches)77%extreme
July Weather30°C (86°F)65 mm (2.6 inches)71%extreme
August Weather30°C (86°F)86 mm (3.4 inches)67%extreme
September Weather27°C (81°F)100 mm (4.0 inches)69%very high
October Weather21°C (70°F)117 mm (4.6 inches)73%very high
November Weather15°C (59°F)69 mm (2.7 inches)82%high
December Weather12°C (54°F)92 mm (3.6 inches)87%moderate

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