It happened just before 2 p.m. on the 100 block of Eldridge Avenue in Lawrence Township, New Jersey.
Authorities say the child was playing in a backyard when the windy weather snapped a tree limb.
The limb then reportedly fell and fatally injured the child.
Police have also not released the child's identity.
Mercer County officials are investigating the incident. Anyone with information is asked to contact the police.