Denver Weather in September

September offers excellent weather for Denver, Colorado. It is the year's sunniest month. And the days have cooled down from the rest of summer.

This page gives detailed information on the typical September temperature, precipitation, snow, sun, humidity, wind and storms for Denver. The numbers here are historical averages based on climate data gathered in the Denver community of Stapleton.

Temperature Weather iconTemperature

80 °F September average high 27 °C
48 °F September average low 9 °C
17 days 80 °F max. or more (27 °C)
17 days 50 °F min. or less (10 °C)

Nearly every day in September warms to over 60 degrees Fahrenheit (16 degrees Celsius) in Denver. The city averages four days this month when the thermometer reaches into the 90s °F (over 32 °C). Temperatures above 100 °F (38 °C) are not expected here during September.

At night, the thermometer dips to 40 °F (7 °C) or below on 4 days. September occasionally has a night of frost.

Rainy Weather iconPrecipitation

1.5 in total precipitation 38 mm
6 days of rain or snowfall

Half the time, Denver receives 0.5 to 1.6 inches (14 to 41 mm) of precipitation in September. One in four years has drier weather, while another one in four is wetter.

Snowy Weather iconSnow

0.8 in total snowfall 2 cm
1 day with new snow

Most years, Denver receives no snow in September.

Sunny Weather iconSun

74 % sunshine
13 days clear skies

September is Denver's sunniest month of the year. The sun's rays reach the ground here during 74 percent of daylight hours on average, for a total of 276 hours in the month. Typically on 13 days this month the sky is mainly clear, with at most 30 percent cloud cover.

Sunlight in September at Denver lasts for 12 hours and 25 minutes a day on average. The longest day of the month is the 1st with 13 hours and 2 minutes of daylight. By the end of the month, the days have shortened to 11:48 from sunrise to sunset. These durations can vary by a minute or two from year to year.

Humid Weather iconHumidity

50 % September average humidity

The relative humidity in Denver during September usually peaks at 69 percent in the morning then drops to 31 percent by early afternoon.

Local Time2 am5 am8 am11 am2 pm5 pm8 pm11 pm
Humidity % 65 69 55 38 31 34 50 59

Windy Weather iconWind

8.0 mph September wind speed average 12.9 kph

September is less windy than most other months in Denver.

Stormy Weather iconStorms

1 day rainfall of 0.5 inches (13 mm) or more
4 days with thunderstorms in September

Every few years, Denver gets an inch (2.5 cm) or more of fresh snow in one day during September.


The weather data here are long-term averages provided by the US National Centers for Environmental Information (NCEI). Temperature and precipitation are 1991-2020 normals while humidity and thunderstorms are 1961-1990 normals.

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