Denver
Colorado, USA
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Denver, CO

The colorful sky above the sunlit Denver city, Colorado in autumn, with a water body surrounded by trees, and majestic skyscrapers afar
The colorful sky above the sunlit Denver city, Colorado in autumn, with a water body surrounded by trees, and majestic skyscrapers afar
September is one of the best times to visit Denver and is the gateway to the pleasant autumn season. Average temperatures are in the range of 48°F (8.9°C) to 77°F (25°C) during the sunniest period of the year. The sunshine lasts for a daily 12 hours and reaches the ground during 74% of daylight hours.
The aspens turn colors by late September, and it is a great time to traverse the scenic interstate 70 to the Rockies amid drizzling rain.
The summer crowds dwindle by September as a new set of visitors arrive to experience the beautiful fall colors.

What is the temperature in September in Denver?

The average high-temperature, in September, is 78.4°F (25.8°C), while the average low-temperature is 48.4°F (9.1°C).

What is the average humidity in September in Denver?

In Denver, Colorado, the average relative humidity in September is 50.1%.

How many days does it rain in September in Denver?

In Denver, Colorado, in September, during 6.5 rainfall days, 1" (24.4mm) of precipitation is typically accumulated.

When does it start to snow in Denver?

September is the first month it typically snows in Denver. Throughout September, in the average 0.5 snowfall days, it receives 1.3" (33mm) of snow.

How many hours of daylight does Denver have in September?

In September, the average length of the day in Denver is 12.4h.

How long on average sun shines in September in Denver?

The average sunshine in September in Denver, Colorado, is 9.1h.

What is the UV index intensity in September in Denver?

In September, the average daily maximum UV index is 7. A UV Index reading of 6 to 7 represents a high hazard to health from the exposure to the Sun's UV rays.
Average temperature in September - Denver, CO
  • Average high temperature in September: 78.5°F

The warmest month (with the highest average high temperature) is July (89.4°F).
The month with the lowest average high temperature is December (42.8°F).

  • Average low temperature in September: 48.3°F

The month with the highest average low temperature is July (58.9°F).
The coldest month (with the lowest average low temperature) is December (17.1°F).

Average humidity in September - Denver, CO
  • Average humidity in September: 50.1%

The month with the highest relative humidity is December (56.6%).
The month with the lowest relative humidity is July (47.8%).

Average rainfall in September - Denver, CO
  • Average rainfall in September: 1"

The wettest month (with the highest rainfall) is July (2.2").
Driest months (with the lowest rainfall) are January, February and December (0.4").

Average rainfall days in September - Denver, CO
  • Average rainfall days in September: 6.5 days

The month with the highest number of rainy days is May (9.4 days).
Months with the lowest number of rainy days are January and December (4.1 days).

Average snowfall in September - Denver, CO
  • Average snowfall in September: 1.3"

The month with the highest snowfall is March (10.7").
Months with the lowest snowfall are June, July and August (0").

Average snowfall days in September - Denver, CO
  • Average snowfall days in September: 0.5 days

The month with the highest number of snowfall days is March (5.8 days).
Months with the lowest number of snowfall days are June, July and August (0 days).

Average daylight in September / Average sunshine in September - Denver, CO
  • Average daylight in September: 12.4h

The month with the longest days is June (Average daylight: 15h).
The month with shortest days is December (Average daylight: 9.4h).

  • Average sunshine in September: 9.1h

Months with most sunshine are June and July (Average sunshine: 10.5h).
The month with least sunshine is December (Average sunshine: 6.3h).

Average UV index in September - Denver, CO
  • Average UV index in September: 7

The month with the highest UV index is July (UV index 11).
Months with the lowest UV index are January and December (UV index 2).