Why does my four year old snore so heavily?

Tonsils or adenoids: Your son should be checked for anything obstructing his airway. This could include tonsils adenoids or allergies or even nasal polyps. Good luck!

adenoids ; tonsils: Most children who snore at this age have enlarged adenoids and/or tonsils. This tissue grow larger in some children and can block the airway at night and cause snoring. Another common cause is allergies causing nasal congestion. Snoring by itself is not dangerous but can affect quality of sleep and daytime functioning in some children. The best thing is to have him evaluated by an ent.