The victims had shelter under a tree during the rains, sources said adding that lightning struck them and and they died on the spot.
They were identified as Rupesh Kujur (25), Tibrius Tirkey (22) and Sanatan Toppo (13), all residents of Khindalal Toli.
Deputy Commissioner Manjunath Bhajantri reached the spot and assured compensation to the family members of the victims.