Geography of Denver, Colorado - Climate

Climate

Denver has a semi-arid climate with four distinct seasons. The weather of the city and surrounding area is influenced by the proximity of the Rocky Mountains to the west. The climate, while generally mild compared to the mountains to the west and the plains further east, can be mildly unpredictable. Measurable amounts of snow have fallen in Denver as late as Memorial Day and as early as Labor Day, though this is extremely rare.

The average temperature in Denver is 50.5°F (10.2°C), and the average yearly precipitation is 14.92 in (379mm). The season's first snowfall generally occurs around October 19, and the last snowfall is about April 27, averaging 61.6 in (156 cm) of seasonal accumulation. Although Denver's Convention and Visitor Bureau claims Denver receives over 300 sunny days a year, according to the National Oceanic and Atmospheric Administration, Denver averages 245 clear and partly cloudy days per year.

Denver's winters are dry and normally mild during the day, and although large amounts of snow can fall on the mountains just west of the city, the effects of orographic lift dry out the air passing over the Front Range shadowing the city from precipitation for much of the season. Additionally, warm chinook winds can occasionally be felt as air passing over the mountains heats as it descends, bringing a melting snow cover and surging temperatures. Nevertheless, winters are generally cold, with the coldest temperature ever recorded in Denver was recorded on January 9, 1875 at −29 °F (−34 °C), though the last time Denver recorded a temperature below −20 °F (−29 °C) was in 1990.

Spring brings with it significant changes as Denver can be affected by air masses on all sides, whether arctic air from the north, which occasionally combines with Pacific storm fronts bringing snow to the city. In fact, March is Denver's snowiest month, averaging 11.7 inches (29.7 cm) of snow. Additionally, warm air from the Gulf of Mexico can bring the first thunderstorms of the season, and continental warm air can bring summer-like warm and dry conditions.

Starting in mid-July, the monsoon brings tropical moisture into the city and with it come occasional short late-afternoon thunderstorms. However, despite this tropical moisture, humidity levels during the day generally remain very low. The average high during July is 88.0 °F (31.1 °C) and the low is 58.7 °F (14.8 °C).

In the autumn, the tropical monsoon flow dies down and as arctic air begins to approach it can combine with moisture from the Pacific Northwest to bring snowfall to the city – November is Denver's second snowiest month, and Denver's greatest recorded snowfall from a single storm, 45.7 inches (116 cm), fell in late autumn from December 1 to December 6, 1913.

In general diurnal temperature range is large, averaging between 26.7 °F (14.8 °C) to 30.1 °F (16.7 °C).

NOTE - the above data were taken at Stapleton Airport until its closure, at which time Denver International Airport became the replacing station