There is a controversy about this event. Some consider Купало day as pagan event (June 20-21, Summer Solstice) and some as Иван Купала day as a Christian church event (July 7 for Orthodox Church, June 24 for all others)
Apparently you mean the pagan event. It is banned by Orthodox church, not a big event in Russia, IMHO
It is very interesting that it is big-big holiday in Scandinavia Any hops over fire, Hanna?