September Weather in Fairfield, United States

Last updated: June 24, 2025

In September, the average temperature in Fairfield, United States hovers around 21°C (69°F). Expect a minimum drop to 6°C (43°F) and a peak of 34°C (94°F), offering a wide range of climatic experiences. The region sees about 121 mm (4.8 in) of precipitation spread across 8 days, contributing to an average humidity of 78%. Whether you're enjoying sunny afternoons or cozy, rainy evenings, there's plenty to love about this month's weather!

September Temperature in Fairfield

In September, in Fairfield, the average temperature is 21°C (69°F). The maximum can reach 34°C (94°F), while the minimum can be as low as 6°C (43°F). It's an ideal time for travelers to enjoy a mix of warm days and cooler evenings.

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 21°C (69°F), with highs reaching up to 34°C (94°F) and lows dropping to around 6°C (43°F).

Data source: Temperature data for Fairfield generated using information from the Copernicus Climate Change Service.

September Precipitation in Fairfield

In Fairfield in September, the precipitation amount is 121 mm (4.8 in) over the course of 8 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 121 mm (4.8 inches) of precipitation spread over approximately 8 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

September Humidity in Fairfield

In Fairfield in September, humidity is 78%. With an average temperature of 21°C (69°F), this humidity feels like a warm embrace that clings to your skin, making outdoor activities feel more intense and leaving you yearning for refreshing breezes or a cool drink as you explore.

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 78%, offering insight into how humid the weather typically is during this month.

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 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 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 8, which falls under the very high exposure category.

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.
	Temperature	Precipitation	Humidity	UV
January Weather	-4°C (25°F)	52 mm (2.0 inches)	81%	moderate
February Weather	-3°C (27°F)	55 mm (2.2 inches)	81%	moderate
March Weather	5°C (42°F)	91 mm (3.6 inches)	81%	high
April Weather	10°C (51°F)	83 mm (3.3 inches)	82%	very high
May Weather	18°C (64°F)	160 mm (6.3 inches)	78%	very high
June Weather	24°C (75°F)	133 mm (5.2 inches)	81%	extreme
July Weather	25°C (78°F)	70 mm (2.8 inches)	79%	very high
August Weather	24°C (75°F)	73 mm (2.9 inches)	77%	very high
September Weather	21°C (69°F)	121 mm (4.8 inches)	78%	very high
October Weather	12°C (54°F)	124 mm (4.9 inches)	78%	high
November Weather	4°C (40°F)	52 mm (2.0 inches)	87%	moderate
December Weather	0°C (33°F)	43 mm (1.7 inches)	84%	moderate