The 323 reindeer, including 70 young, were found on Friday by a gamekeeper on the Hardangervidda plateau, a national park where Europe’s largest herd of some 10,000 wild reindeer roam freely.
Television footage showed the animals’ dead bodies lying close together on the ground.
“There were very strong storms in the area on Friday. The animals stay close together in bad weather and these ones were hit by lightning,” an official from the Norwegian Environment Agency, Kjartan Knutsen, told AFP.
Reindeer are social creatures and usually move in packs.
“It’s unusual. We’ve never seen anything like this on this scale,” Knutsen said.