How can you tell if your sleeping baby is getting overheated? She may feel very warm behind her neck, her hair may be damp from sweat or her cheeks may become quite red.
A tremendous amount of heat is lost when we sweat and your baby is no exception. Monitor your baby’s temperature closely, unzip their bunting and remove their hat when you put them in the car or go into a warm shop, and bring an extra set of cloths just in case they get sweaty.
From:Traveling with Kids.com.