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 October day warms to over 50 Â°F (10 Â°C) in Denver. The city averages 3 days this month when the thermometer reaches into the 80s Â°F (over 26 Â°C). Temperatures above 90 Â°F (32 Â°C) are not expected here during October. Sometimes in October the mercury remains below freezing for an entire day. On an average of 9 nights, the thermometer dips to freezing or below. About once a decade, weather as cold as 10 Â°F (-12 Â°C) has descended on Denver in October. Half the time, Denver receives 0.5 to 2 inches (11 to 38 mm) of precipitation in October.