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September Weather in Grand Junction, United States

Last updated: June 24, 2025

In September, the average temperature in Grand Junction, United States hovers around 20°C (68°F). However, you might experience a wide range, with minimum temperatures dipping to 4°C (39°F) and maximums soaring up to 36°C (96°F). Be prepared for some rain too, as 108 mm (4.2 in) of precipitation is expected over about 10 days, contributing to an average humidity of 73%.

September Temperature in Grand Junction

In September in Grand Junction, the average temperature is 20°C (68°F). Maximums can reach 36°C (96°F), while minimums can drop to as low as 4°C (39°F). This makes it an ideal time for travelers to experience a mix of warm and cool weather, allowing for a variety of outdoor activities.

September Weather in Grand Junction: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Grand Junction, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Grand Junction, September typically has an average temperature of 20°C (68°F), with highs reaching up to 36°C (96°F) and lows dropping to around 4°C (39°F).
JanFebMarAprMayJunJulAugSepOctNovDec222339496274777368523830
Data source: Temperature data for Grand Junction 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 Grand Junction

In Grand Junction in September, the precipitation amount is 108 mm (4.2 in) distributed over a duration of 10 days.

September Precipitation Trends in Grand Junction

The chart displays monthly precipitation patterns in Grand Junction, 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 Grand Junction, September typically receives around 108 mm (4.2 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec3239766616310184901081233637
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Grand Junction

In Grand Junction in September, humidity is 73%. With an average temperature of 20°C (68°F), this humidity feels like a warm embrace, making outdoor activities somewhat sticky, yet the atmosphere remains pleasant for leisurely strolls and sightseeing.

September Average Humidity in Grand Junction

This chart illustrates the average monthly humidity levels in Grand Junction, 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 Grand Junction is approximately 73%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec78%80%77%78%77%81%81%77%73%75%85%83%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Grand Junction

In Grand Junction 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 Grand Junction.

Maximum UV Index Levels in Grand Junction for September

The chart shows the monthly maximum UV Index (UVI) for Grand Junction 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 Grand Junction typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec35589111098643
Data source: Grand Junction 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 Grand Junction Compares to Other Months

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

This table compares monthly weather conditions in Grand Junction, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-6°C (22°F)32 mm (1.3 inches)78%moderate
February Weather-5°C (23°F)39 mm (1.5 inches)80%moderate
March Weather4°C (39°F)76 mm (3.0 inches)77%moderate
April Weather9°C (49°F)66 mm (2.6 inches)77%very high
May Weather17°C (62°F)163 mm (6.4 inches)77%very high
June Weather23°C (74°F)101 mm (4.0 inches)81%extreme
July Weather25°C (77°F)84 mm (3.3 inches)81%very high
August Weather23°C (74°F)90 mm (3.5 inches)77%very high
September Weather20°C (68°F)108 mm (4.2 inches)73%very high
October Weather11°C (52°F)122 mm (4.8 inches)75%high
November Weather3°C (38°F)36 mm (1.4 inches)85%moderate
December Weather-1°C (30°F)37 mm (1.4 inches)83%moderate

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