Kathy, I have been to Lima and Cusco during late December/early January for a couple weeks. We hiked the Inca trail and stayed in Cusco for about a week. The weather was pleasant and the altitude took a day or two to get used to. In the mountains on the trail the weather was very sporadic. I was hiking in a t-shirt one minute and wearing a mid-weight waterproof parka the next. Beautiful country with friendly people.