September Weather in Thornton, United States

Last updated: June 24, 2025

In September, the average temperature in Thornton, United States hovers around 15°C (59°F), offering a pleasant climate. Be prepared for a temperature range that can dip as low as -4°C (25°F) and soar up to 29°C (85°F). With an average precipitation of 71 mm (2.8 in) spread over about 10 days, expect some showers during your stay. The average humidity sits at a comfortable 71%, making it an ideal time to explore!

September Temperature in Thornton

In September in Thornton, the average temperature is 15°C (59°F), with maximums reaching 29°C (85°F) and minimums dropping as low as -4°C (25°F). This makes for a diverse range of weather, so be sure to pack accordingly for your travels!

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

The chart illustrates September temperature patterns in Thornton, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Thornton, September typically has an average temperature of 15°C (59°F), with highs reaching up to 29°C (85°F) and lows dropping to around -4°C (25°F).

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

September Precipitation in Thornton

In Thornton in September, the precipitation amount is 71 mm (2.8 in) over a duration of 10 days.

September Precipitation Trends in Thornton

The chart displays monthly precipitation patterns in Thornton, 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 Thornton, September typically receives around 71 mm (2.8 inches) of precipitation spread over approximately 10 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 Thornton

In Thornton in September humidity is 71%. With an average temperature of 15°C (59°F), this humidity feels like a damp embrace, making outdoor activities slightly uncomfortable and encouraging travelers to seek shade or indoor attractions to escape the muggy air.

September Average Humidity in Thornton

This chart illustrates the average monthly humidity levels in Thornton, 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 Thornton is approximately 71%, 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 Thornton

In Thornton in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Thornton.

Maximum UV Index Levels in Thornton for September

The chart shows the monthly maximum UV Index (UVI) for Thornton 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 Thornton typically reaches 7, which falls under the high exposure category.

Data source: Thornton 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 Thornton Compares to Other Months

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

This table compares monthly weather conditions in Thornton, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-8°C (18°F)	85 mm (3.4 inches)	86%	moderate
February Weather	-6°C (21°F)	86 mm (3.4 inches)	84%	moderate
March Weather	-2°C (28°F)	75 mm (2.9 inches)	82%	high
April Weather	5°C (41°F)	129 mm (5.1 inches)	80%	very high
May Weather	12°C (53°F)	98 mm (3.9 inches)	72%	very high
June Weather	17°C (63°F)	105 mm (4.1 inches)	72%	very high
July Weather	20°C (68°F)	135 mm (5.3 inches)	67%	very high
August Weather	19°C (66°F)	99 mm (3.9 inches)	66%	very high
September Weather	15°C (59°F)	71 mm (2.8 inches)	71%	high
October Weather	8°C (47°F)	143 mm (5.6 inches)	78%	moderate
November Weather	0°C (33°F)	119 mm (4.7 inches)	84%	moderate
December Weather	-5°C (23°F)	113 mm (4.5 inches)	81%	low