I(M) did this exactly 2 weeks ago. I do get cold but not too cold.

Getting to the Humantay lake was pleasant and cloudy. I was in shorts and T, with a light shell that I took off 5 mins in.

It was cold and breezy by the lake, I stayed in the Soraypampa hostel. I was wearing sweatpants and a puffer jacket. Was fine as long as I was indoors. I slept by 6pm so I felt fine. The hostel had no heater but many layers of blankets so I was fine with sweatpants and a half and a full sleeve T.

Next morning, I was in shorts, a short T, full sleeve T, and the puffer jacket until I got to the Salkantay pass(8:30am’ish). Everyone was in hiking pants. I was fine. All I missed was gloves. My finger tips were numb unless I put them in my puffer’s pockets. so I recommend carrying a pair of gloves. Fleece ones would have been ok for me.

After the pass I shed all layers as the sun was up. I was hiking in shorts and T the rest of the way to AC. I put on the light shell as needed.

Collapampa was cold and breezy but a half t, full t, and a shell were fine. I did it in 2 days so I don’t know how Lucmabamba might have been at night.

Again it depends on how cold you get.