What is the most likely reason for Leadvill Colorado being colder then Denver Colorado?

The most likely reason for Leadville, Colorado being colder than Denver, Colorado is its higher elevation. Leadville is located at an elevation of 10,200 feet, while Denver is located at an elevation of 5,280 feet. As elevation increases, the air temperature decreases. This is because the air is less dense at higher elevations, so it cannot hold as much heat. Additionally, Leadville is located in the Rocky Mountains, which are known for their cold weather.