Police said a man, his two daughters and a son were crushed to death under a tree beneath which they were sleeping at Kona village in Chatra district.
Three members of a family were struck dead by lightning at Baghtand in Dhanbad district, police said.
The fierce storm hit around 4.30 am and a large number of electricity poles and hundreds of trees were uprooted in Ranchi, Jamshedpur, Hazaribagh, Latehar and some other districts.
In another incident, a 32-year-old farmer, identified as Neel Ratan Pal, was killed as lightning struck him while he was in his paddy field at Dhadhika village in East Singhbhum district, police said.