range from mild to moderately cold, 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; from December to February there is an average of 12−18 days of + highs and 1−3 days of above-freezing lows per month. The coldest temperature ever recorded in Denver was recorded on January 9, 1875, at , though the last time Denver recorded a temperature below was December 22, 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. As reported at Denver International, March is the second snowiest month, averaging 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. The last freeze of the season on average falls on May 6. Starting in mid-July, the monsoon brings tropical moisture into the city, and with it comes occasional short late-afternoon thunderstorms. However, despite this tropical moisture, humidity levels during the day generally remain very low, and lows rarely remain at or above . There are 38 days of + highs per year, though + highs are not seen annually. The average window for temperatures reaching the former threshold is June 4 thru September 7. 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 third snowiest month, and both the greatest snowfall from a single storm and daily snow depth on record occurred before the Winter Solstice. In general diurnal temperature range is large, averaging between . Extreme statistics (since 1872 unless otherwise indicated): All-time record high: on August 8, 1878, July 20, 2005, June 25−26, 2012, and June 28, 2018. The All-time record low: on January 9, 1875 Lowest daily maximum: on February 3, 1883 Highest daily minimum: on July 3, 1881 Highest daily average: on