[lostalex]

When you're not using your hand usually all of your fingers come together and and stay close together and also curl p towards the inside of your hand. Most people use their left hand much less. When you are using your hand the fingers are more separate therefore there is more surface area to lose body heat. Usually the right hand.

Also a lot of people put their non dominant hand into their crotch when they are not using it, which also makes it warmer.