September Weather in Monticello, United States

Last updated: June 24, 2025

In September, the average temperature in Monticello, United States hovers around 18°C (65°F). Expect a temperature range that can dip as low as -1°C (31°F) and soar up to 34°C (94°F). With an average precipitation of 26 mm (1.0 in) spread over 4 days, you might want to keep an umbrella handy. The average humidity sits at a comfortable 59%, making it a pleasant time to explore!

September Temperature in Monticello

In September in Monticello, the average temperature is 18°C (65°F), with maximums reaching up to 34°C (94°F) and minimums occasionally dropping to as low as -1°C (31°F). Be sure to pack accordingly for your travels, as the temperature can vary significantly during this time.

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

The chart illustrates September temperature patterns in Monticello, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Monticello, September typically has an average temperature of 18°C (65°F), with highs reaching up to 34°C (94°F) and lows dropping to around -1°C (31°F).

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

September Precipitation in Monticello

In Monticello in September, the precipitation amount is 26 mm (1.0 in) over the course of 4 days.

September Precipitation Trends in Monticello

The chart displays monthly precipitation patterns in Monticello, 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 Monticello, September typically receives around 26 mm (1.0 inches) of precipitation spread over approximately 4 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 Monticello

In Monticello in September, humidity is 59%. With an average temperature of 18°C (65°F), this humidity feels like a gentle embrace, providing a refreshing atmosphere that's ideal for exploring the sights without feeling too hot or sticky.

September Average Humidity in Monticello

This chart illustrates the average monthly humidity levels in Monticello, 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 Monticello is approximately 59%, 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 Monticello

In Monticello 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 Monticello.

Maximum UV Index Levels in Monticello for September

The chart shows the monthly maximum UV Index (UVI) for Monticello 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 Monticello typically reaches 10, which falls under the very high exposure category.

Data source: Monticello 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 Monticello Compares to Other Months

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

This table compares monthly weather conditions in Monticello, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-3°C (27°F)	35 mm (1.4 inches)	85%	moderate
February Weather	0°C (31°F)	43 mm (1.7 inches)	86%	high
March Weather	5°C (41°F)	53 mm (2.1 inches)	76%	very high
April Weather	10°C (50°F)	18 mm (0.7 inches)	69%	very high
May Weather	15°C (59°F)	28 mm (1.1 inches)	53%	extreme
June Weather	22°C (72°F)	10 mm (0.4 inches)	40%	extreme
July Weather	24°C (76°F)	32 mm (1.3 inches)	36%	extreme
August Weather	23°C (74°F)	21 mm (0.8 inches)	44%	extreme
September Weather	18°C (65°F)	26 mm (1.0 inches)	59%	very high
October Weather	10°C (50°F)	37 mm (1.4 inches)	74%	high
November Weather	4°C (40°F)	19 mm (0.8 inches)	83%	moderate
December Weather	-2°C (29°F)	34 mm (1.3 inches)	85%	moderate