Denver Weather in September
United States · Humid Continental climate · Data averaged from 2020-01-01 to 2024-12-31 (5 years)
September in Denver sees average temperatures ranging from a low of 10.6°C (51.1°F) to a high of 28.2°C (82.8°F), with a mean of 19.1°C (66.4°F). Compared to the annual average of 10.0°C (50.0°F), this month is 9.1°C warmer than the yearly norm. Precipitation averages 22.5mm, making it approximately 11.0mm drier than the monthly average of 34.0mm. The city receives an average of 11.0 hours of sunshine per day during September, with relative humidity averaging 42.1%. Wind speeds reach an average maximum of 17.7 km/h. Snowfall averages 2.3cm during September, which can affect travel plans and outdoor activities. For travelers, this month offers a temperature experience in Denver, with drier-than-average conditions compared to the rest of the year.
Denver's mile-high altitude creates a unique climate with low humidity and intense sunshine. I've studied the data and found that the city receives over 300 days of sunshine annually, making it one of the sunniest major US cities. The best time for outdoor activities is May to October, when temperatures are warm and the Rocky Mountains are accessible. The winters are cold but dry, with plenty of sunshine.
September vs Adjacent Months
| Metric | August | September | October |
|---|---|---|---|
| Mean Temp | 23.4°C (74.1°F) | 19.1°C (66.4°F) | 11.2°C (52.2°F) |
| Rainfall | 27.8mm | 22.5mm | 17.6mm |
| Sunshine | 12.0 hrs | 11.0 hrs | 9.8 hrs |
| Humidity | 44.7% | 42.1% | 45.7% |
| Wind | 19.5 km/h | 17.7 km/h | 17.4 km/h |
| Rainy Days | 11.0 | 5.8 | 3.6 |
| Snowfall | 0.0 cm | 2.3 cm | 4.5 cm |
Seasonal Context
September falls in Autumn in the Northern Hemisphere. Autumn sees temperatures gradually cooling from summer highs. For travelers visiting Denver in September, the data indicates favorable conditions based on the combination of temperature, precipitation, and daylight hours.
Frequently Asked Questions
What is the average temperature in Denver in September?
The average temperature in Denver during September ranges from 10.6°C (51.1°F) to 28.2°C (82.8°F), with a mean of 19.1°C (66.4°F).
How much does it rain in Denver in September?
Denver receives an average of 22.5mm of precipitation in September, spread across approximately 5.8 rainy days.
What should I pack for Denver in September?
Based on September weather data, pack layers including light jackets and t-shirts, plus an umbrella.
Is September a good time to visit Denver?
September is a good time to visit Denver, with comfortable temperatures and manageable rainfall.
Other Months for Denver
Cities with Similar September Climate (Humid Continental)
Data Source: Open-Meteo historical archive (2020-01-01 to 2024-12-31). Daily measurements aggregated into monthly climate normals. Coordinates: 39.74°, -104.99°. Timezone: America/Denver. Last updated: 2026-07-30.