How to do that? The American Academy of Pediatrics recommends dressing young children in one more layer of clothing than an adult would wear in the same conditions. Start with a thin inner layer to wick moisture away from the skin. Avoid cotton, which soaks up sweat and holds it against the skin, accelerating heat loss; try a lightweight polyester or polypropylene fabric instead. Add two insulating middle layers (maybe a long sleeved top and leggings) of similar materials, keeping them a little loose to trap insulating air between fibers. Top it all off with a wind and waterproof outer shell.