The temperature is usually between 45-55 in the mornings and at night and between 65-80 during the day. With that being said dress in layers. You will want a sweater or light jacket for mornings or evenings and possibly during the day if you are in the shade. It's also a good idea to bring a rain coat. Aspen and Snowmass are very relaxed and casual towns. With the exception of a few restaurants you can wear athletic wear or "mountain casual" clothes ( jeans, hats, boots) almost everywhere. We recommend wearing sturdy, flat , comfortable shoes.