If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Aspen: 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, March, January and December, with each month seeing an average of 38 cm of snowfall.