Found this answer to your question:
What to wear
Dressing an infant involves the same number of layers as you would wear plus maybe an additional one (such as a onesie) if cooler weather. I am a big fan of the car seat cover in the winter, which only exposes the face, allows you to stuff it with blankets and does away with the need for dressing the infant in a coat. Always wear a hat outside in cold weather.
Overdressing or overbundling an infant can lead to a false fever. In hot, humid weather, dress newborns in lighter clothing since they lack the ability to sweat and may get prickly rash.