It's one of the great mysteries in life: Two people, sleeping in the same tent and using the same type of bag, will have a totally different night's sleep. One camper sweats; the other shivers.
Dr. Gordon Giesbrecht, Ph.D. and professor of thermophysiology at the University of Manitoba, offers a few reasons why. First, people have different perceptions of cold. Even if two campers are in the exact same climate with the same core temperature, one may be less tolerant of cold weather and therefore more uncomfortable. It's not surprising that someone from California will feel colder than the guy from North Dakota. But give it a few days and the Popsicle can acclimate, says Dr. Giesbrecht.
Gender plays a role, too: Women have it tougher than men in cooler climes. A recent study found that women's core temperatures are slightly higher than men's, which actually means they get a little colder in the tent because of vasoconstriction, a phenomenon in which blood vessels constrict and decrease blood flow to the skin.
Lastly, cold sleepers simply may not prepare themselves for a good night's sleep. Campers often overdress when hopping in the sack and then sweat later in the night, which puts water vapor in their bags and reduces warmth.