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.
The sun's rays reach the ground in Denver during 71 percent of daylight hours on average in July, for a total of 322 hours in the month. Typically on 9 days this month the sky is mainly clear, with at most 30 percent cloud cover. Sunlight in July at Denver lasts for 14 hours and 38 minutes a day on average.