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.
Sunlight in August at Denver lasts for 13 hours and 40 minutes a day on average. The longest day of the month is the 1st with 14 hours and 13 minutes of daylight. By the end of the month, the days have shortened to 13:05 from sunrise to sunset. These durations can vary by a minute or two from year to year.