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.
Nearly every day in April warms to over 40 Â°F (4 Â°C) in Denver. The city averages 8 days this month when the thermometer reaches into the 70s Â°F (over 21 Â°C).There can even be a day or two of 80-degree F (over 26 Â°C) weather. But some years can also see a day this month when the temperature never rises above freezing.early every day in April warms to over 40 Â°F (4 Â°C) in Denver. The city averages 8 days this month when the thermometer reaches into the 70s Â°F (over 21 Â°C).