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September Weather in Monticello, United States

Last updated: June 24, 2025

In September, the average temperature in Monticello, United States is a warm 27°C (80°F). Visitors can expect a range, with temperatures dipping to a cool 12°C (53°F) at night and soaring up to 39°C (103°F) during the day. Expect some rainfall, averaging 72 mm (2.8 in) over 8 days, and be prepared for moderate humidity at around 73%.

September Temperature in Monticello

In September in Monticello, the average temperature is 27°C (80°F). Maximums can reach 39°C (103°F) and minimums can be as low as 12°C (53°F). Travelers should be prepared for warm days and cooler evenings, making it an ideal destination for those who enjoy a mix of summer warmth and comfortable night 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 27°C (80°F), with highs reaching up to 39°C (103°F) and lows dropping to around 12°C (53°F).
JanFebMarAprMayJunJulAugSepOctNovDec485261657480838280695552
Data source: Temperature data for Monticello generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Monticello

In Monticello in September, the precipitation amount is 72 mm (2.8 in) over the course of 8 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 72 mm (2.8 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec125199141176125106107917213191128
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Monticello

In Monticello in September humidity is 73%. With an average temperature of 27°C (80°F), this humidity feels like a warm, enveloping blanket that can make traveling feel sticky and slightly uncomfortable, prompting frequent breaks in the shade and plenty of hydration.

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 73%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%83%80%82%83%80%80%75%73%76%84%88%
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.
JanFebMarAprMayJunJulAugSepOctNovDec478111112121110864
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.
 TemperaturePrecipitationHumidityUV
January Weather9°C (48°F)125 mm (4.9 inches)84%moderate
February Weather11°C (53°F)199 mm (7.8 inches)83%high
March Weather16°C (61°F)141 mm (5.6 inches)80%very high
April Weather18°C (65°F)176 mm (6.9 inches)82%extreme
May Weather23°C (74°F)125 mm (4.9 inches)83%extreme
June Weather27°C (80°F)106 mm (4.2 inches)80%extreme
July Weather28°C (83°F)107 mm (4.2 inches)80%extreme
August Weather28°C (83°F)91 mm (3.6 inches)75%extreme
September Weather27°C (80°F)72 mm (2.8 inches)73%very high
October Weather21°C (69°F)131 mm (5.2 inches)76%very high
November Weather13°C (56°F)91 mm (3.6 inches)84%high
December Weather11°C (52°F)128 mm (5.0 inches)88%moderate

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