It is hard to keep an infant warm and comfortable in winter. The following tips may be of some use to parents who have infants and young children:
1) In the car seat: Bulky clothes are not safe for car seats as they interfere with a harness. Instead have the baby wear sleeper (or well-fitted fleece suit) and a hat, and place blankets over the top.
2) In a carrier: Keeping baby’s airway clear is of outmost importance. If the baby is in a fitted fleece suit, check his hands and feet often to be sure they are warm enough.
3) In a stroller: Dress up the baby in layers. Start with a long-sleeved onesie, pants and socks or a sleeper, and then add a sweater or zip-up sweatshirt and, finally, a snowsuit. Ears, hands and feet are most at risk for frostbite, so make sure they’re well covered.
http://www.todaysparent.com/baby/baby-health/how-to-dress-your-baby-for-winter/