Best Time Of The Year. July and November are good months to book flights. They tend to be months when other people are not planning their holidays, so they feature a low demand for airline tickets and consequent low prices. September, after the summer holidays, and January, after Christmas and Thanksgiving holidays, are months to avoid.
Weather in Denver in September. The average maximum daytime temperature in Denver in September is a warm 25Â°C (77Â°F). There are usually 9 hours of bright sunshine each day, which represents 73% of the 12 hours of daylight. Expect 30mm (1.2 inches) of rainfall across the whole of September with 7 days with some rain falling.
Denver, Colorado Climate & Temperature. 1  Denver, Colorado, Usa is at 39 46'N, 104 52'W, 1612 m (5289 ft). 2  See map. 3  Denver, Colorado has a humid subtropical climate that is mild with no dry season, constantly moist (year-round rainfall).4  Summers are hot and muggy with thunderstorms. The mean temperature is 10.1 degrees Celsius (50.2 degrees Fahrenheit). 2  See the temperatures page for a monthly breakdown and the fixed scale graph. 3  Average monthly temperatures vary by 24.4 Â°C (43.9Â°F). 4  This indicates that the continentality type is continental, subtype subcontinental.