Although these sheets are about as thin as a piece of paper, they are quite warm. Since they're polyester they do not breathe and therefore maintain your body heat. They are good for a fall or winter set, and are much less expensive than flannel- they will weigh you down less as well. The other benefit is that microfiber is virtually stain proof and will also not wrinkle. The downside is that they are very warm so in the summer time they might cause you to break out into a sweat. Otherwise, these are great sheets and very inexpsensive.