I bought an underquilt rated to 40 degrees, as I tend to get hot at night. I used in on several nights when the temperatures got down to about 45-55. There was no wind on any of the nights, but I froze every night and barely slept. (Yes, I had it cinched all the way shut.) In addition to using this underquilt, I put on a long-sleeve shirt, down jacket, hat, gloves, silk underwear, rain pants and socks, all in an effort to stay warm. But nothing worked. BTW, I also purchased a sleeping quilt for use in a tent at the same time. It was mainly for husband, and he asked for one rated to 20 degrees. That sleeping quilt worked well in similar weather, although it was used in tandem with a sleeping pad. Perhaps I should have ordered a warmer underquilt. But since I sleep warm, I thought a 40-degree quilt used on 45-55-degree nights should work well for me. It was a very expensive error.