Their friend found them on the floor after noting that they had been in the sauna for far too long and deciding to check on them.
While sauna deaths are rare, they do occur: A 2008 study published in the Journal of Forensic Sciences looked at sauna-related fatalities between 1990 and 2002 in Finland and found an annual death rate of less than two per 100,000 inhabitants.
While the temperature of the sauna the women were using in the Czech Republic hasn't been reported, study found heat exposure was behind a quarter of Sauna deaths.
Saunas and Finland were under the microscope once again in 2010, when a finalist at the World Sauna Championships there collapsed and died after spending six minutes in a 230-degree Fahrenheit sauna.
While such temperatures might seem uncommon outside of Finland, an organizer told the BBC at the time that "It is not so unusual" here. The competition was permanently ended due to Russian Vladimir Ladyzhensky's death.