Very, very warm! This top/bottom set was exactly what I needed during my mountain vacation during the winter! I honestly don't know how I would have survived the nights without these as my pajamas (there was no heat other than fireplace in our cabin). I probably could have worn these under some of my clothes for added warmth during the day, but I didn't really need it during the sunny daytime hours, and I don't like having added bulkiness, so I didn't bother, but using these as pajamas was perfect!!! I was also very grateful that these arrived so quickly- since they were a last minute purchase!