Yes, it is true in Iceland people leave their babies in freezing temperature. In Iceland, it is very common to let babies nap outdoors in the cold. It is because they want their immune system to build stronger. Here are some other reasons why they do this:
Parents in Iceland believe that cold air strengthens babies' immunity, improves sleep, and boosts their lung health.
In the cold, babies often sleep longer and deeper when outside. The cool, clean air calms their nervous system and supports their natural sleep rhythms.
In Iceland (and other Nordic countries), strollers are parked outside restaurant and homes. It is the part of their culture. They spend their time outdoor in cooler air. It helps both adults and babies feel better and sleep deeper.
Nordic people cover their babies in wool layers, and they monitor the temperature. They stay nearby of babies.
With this activity, babies take fresh air that boosts their immunity, regulates sleep, and calms their nervous system.