Judge how to dress your baby by your comfort level. A temperature that is comfortable for you will also be comfortable for your baby.
In the summer: Dress your baby in cool, lightweight clothing. When you are outdoors, put a wide-brimmed hat on your baby. Be sure to keep your baby out of direct sunlight. Use sunscreen (SPF 30 or higher) on your infant if outside, even on cloudy days.
In the winter: Dress your baby in layers. Be sure not to overdress your baby.