I took the Icebreaker lightweight merino wool tops and bottoms to the Pyrenees last week and had the normal mixed bag of weather. It was great on the wet/cold days but we had a couple of days of 30 degrees, when it was too warm. However, I was wearing a laminate suit with pretty good venting but I was still too hot. I think it would have been better with my Revit Sand 3. Next time I'm going to take a mixture of synthetic and Merino wool baselayers.