September Weather in Union, United States

Last updated: June 24, 2025

In September, the average temperature in Union, United States hovers around 21°C (69°F), creating a pleasant atmosphere for visitors. Temperatures can vary, dipping to a minimum of 5°C (41°F) and peaking at a maximum of 34°C (94°F). Expect around 86 mm (3.4 in) of precipitation spread over 7 days, contributing to an average humidity level of 73%.

September Temperature in Union

In September in Union, the average temperature is 21°C (69°F), with maximums reaching 34°C (94°F) and minimums dropping as low as 5°C (41°F). This makes it a great time for travelers to enjoy a variety of outdoor activities while being prepared for some temperature fluctuations.

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

The chart illustrates September temperature patterns in Union, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Union, 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 5°C (41°F).

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

September Precipitation in Union

In Union in September, the total precipitation amount is 86 mm (3.4 in) over a span of 7 days.

September Precipitation Trends in Union

The chart displays monthly precipitation patterns in Union, 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 Union, September typically receives around 86 mm (3.4 inches) of precipitation spread over approximately 7 days.

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

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Millimeters (mm) Inches (in)

September Humidity in Union

In Union in September, humidity is 73%. With an average temperature of 21°C (69°F), this humidity feels like a warm, sticky embrace, making outdoor activities somewhat stifling and travel a bit more challenging, as the air is dense and can leave you feeling fatigued more quickly.

September Average Humidity in Union

This chart illustrates the average monthly humidity levels in Union, 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 Union is approximately 73%, 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 Union

In Union 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 Union.

Maximum UV Index Levels in Union for September

The chart shows the monthly maximum UV Index (UVI) for Union 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 Union typically reaches 8, which falls under the very high exposure category.

Data source: Union 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 Union Compares to Other Months

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

This table compares monthly weather conditions in Union, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-1°C (31°F)	72 mm (2.8 inches)	88%	moderate
February Weather	1°C (34°F)	97 mm (3.8 inches)	88%	moderate
March Weather	6°C (42°F)	106 mm (4.2 inches)	87%	high
April Weather	11°C (52°F)	98 mm (3.9 inches)	85%	very high
May Weather	18°C (64°F)	129 mm (5.1 inches)	81%	very high
June Weather	22°C (72°F)	120 mm (4.7 inches)	82%	very high
July Weather	24°C (76°F)	100 mm (3.9 inches)	81%	very high
August Weather	23°C (74°F)	90 mm (3.5 inches)	73%	very high
September Weather	21°C (69°F)	86 mm (3.4 inches)	73%	very high
October Weather	14°C (58°F)	99 mm (3.9 inches)	78%	high
November Weather	5°C (42°F)	94 mm (3.7 inches)	89%	moderate
December Weather	2°C (36°F)	87 mm (3.4 inches)	87%	moderate