You certainly don’t want a newborn to be cold. On the other hand, you don’t want the baby to be overdressed and get too hot. Since there’s a link between heat stress and the risk of sudden infant death syndrome (SIDS), this is really something to pay attention to. In the summer, this risk may be higher. Dress your newborn in lightweight clothing and keep blankets and other items out of its crib. Take care to keep the room temperature comfortable as well, and you’ll help your newborn sleep soundly and safely during the warm months of the year.
Use lightweight clothing and breathable fabric. Light fabrics like cotton will keep your baby cool. Avoid heavy fabrics like wool or flannel. Short-sleeved onesies are usually fine in the summer
Dress your baby in newborn sleepwear, if possible. Infant sleepwear is manufactured from approved materials, and is designed to fit safely. If you can find newborn summer sleepwear, dress your baby in this at night and nap times
Choose clothes that will keep your newborn’s face clear. Avoid clothing with hoods, high collars, or other parts that might cover the baby’s face while it sleeps. That way it will stay cooler and be able to breathe safely
Do not cover the infant’s head. An infant regulates its body temperature primarily through its head. Many people like to dress newborns in a cap for protection or comfort, but putting one on an infant sleeping in the summer can quickly make it overheat
Use a sleepsack rather than a blanket. Experts recommend not putting a blanket in a newborn’s crib because it is a suffocation risk. A sleepsack (wearable blanket), however, wraps safely and securely around the baby with velcro or snaps, removing this risk. However, you should remove the sleep sack if the baby gets fussy or seems hot.