More than 500 people were attending the event in a village near the city of Schwerin when lightning struck a group of trees and a nearby switch box on the village fairground.
Police spokesman Joerg Bruhn said many visitors at the fairground suffered burns and were treated for shock. Two rescue helicopters were called to the village of Dabel as well as several ambulances.
On Father's Day in Germany, men traditionally go on day trips or simply get together to drink lots of beer, without their families.
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