Rescuers in northern Poland said they had to force their way through "kilometers" of fallen trees in the Tuchola Forest to reach the site of Friday night's tragedy.
More storms were forecast Saturday after unusually high temperatures for Poland that reached 35 to 38 degrees Celcius (95 to 100 degrees Fahrenheit) on Friday.
In Tuchola Forest, the girls aged 13 and 14 were killed as they sheltered in their tent during the severe storm conditions.
Adam Kralisz, Lodz region scouting chairman, told private broadcast Polsat television that conditions were horrendous.
"We had to force out way for kilometers through the forest, among falling trees," Kralisz said.
Some 20 other scouts with injuries were evacuated to local hospitals.
At least 34 people injured
Other Polish broadcasters, TVP Info and TVN24, said three other people were killed by storm-topped trees, including a 58-year-old woman crushed when a tree fell on her house at Konarzyny, southwest of Danzig.
In total, Polish authorities said at least 34 people, including the scouts, had been injured and warned that casualty figures could rise.
The regional crisis center in Danzig said at least 170,000 people had been left without power and 800 buildings had been damaged across Poland's north and west.
News agencies put the number of outages at 340,000 households. Polish Prime Minister Beata Szydlo promised at a crisis meeting that government would provide help for all those in need.
Severe weather to the south in the Czech Republic also left at least 80 houses damaged, according to the news agency CTK.
ipj/jlw (Reuters, dpa, AP)