September Weather in Monticello, United States

Last updated: June 24, 2025

In September, the average temperature in Monticello, United States is a pleasant 21°C (70°F). Expect fluctuations, with minimums dipping to 5°C (41°F) and maximums soaring to 34°C (93°F). Rainfall is modest, averaging 61 mm (2.4 in) over 9 days, while the humidity lingers at a comfortable 78%.

September Temperature in Monticello

In September in Monticello, the average temperature is 21°C (70°F). Maximums can reach 34°C (93°F), while minimums can drop as low as 5°C (41°F). This makes it an ideal time for travelers to enjoy a variety of outdoor activities while being prepared for both warm and cooler temperatures.

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 21°C (70°F), with highs reaching up to 34°C (93°F) and lows dropping to around 5°C (41°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 61 mm (2.4 in) spread over 9 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 61 mm (2.4 inches) of precipitation spread over approximately 9 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 Monticello

In Monticello in September, humidity is 78%. With an average temperature of 21°C (70°F), this humidity feels like a warm, enveloping blanket that can leave travelers feeling sticky and slightly fatigued, making it important to stay hydrated and take frequent breaks from outdoor activities.

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 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 Monticello

In Monticello 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 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 8, 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	-2°C (29°F)	74 mm (2.9 inches)	85%	moderate
February Weather	-1°C (31°F)	77 mm (3.0 inches)	85%	moderate
March Weather	5°C (42°F)	103 mm (4.0 inches)	86%	high
April Weather	11°C (51°F)	97 mm (3.8 inches)	87%	very high
May Weather	18°C (64°F)	157 mm (6.2 inches)	81%	very high
June Weather	23°C (74°F)	97 mm (3.8 inches)	82%	very high
July Weather	25°C (77°F)	99 mm (3.9 inches)	81%	very high
August Weather	23°C (74°F)	105 mm (4.1 inches)	79%	very high
September Weather	21°C (70°F)	61 mm (2.4 inches)	78%	very high
October Weather	14°C (57°F)	110 mm (4.3 inches)	81%	high
November Weather	5°C (41°F)	74 mm (2.9 inches)	89%	moderate
December Weather	2°C (35°F)	62 mm (2.4 inches)	86%	low