You might spend a lot of your holiday inside, but if you're planning to venture beyond the casino, looking at local weather trends is a good idea. The hottest months are usually July and August, with an average temperature of 13°C, while the coldest months are December and January, with an average of -8°C. The snowiest months in Aspen are February, April, March and January, with each month seeing an average of 43 cm of snowfall.