The sell-out "Rock am Ring" festival, now in its 31st year and with the Red Hot Chili Peppers and Black Sabbath at the top of the billing this year, takes place at the airport in Mendig, near the Nuerburgring motor racing track.
Festival organizers told a news conference that performances would resume after the storm blew over, and said they had warned some 92,500 participants before arriving to be prepared for bad weather.
"We are not considering cancelling the festival," said spokeswoman Katharina Wenisch.
A spokesman for the German Red Cross said 71 people were injured during lightning strikes on Friday, including eight who had to be hospitalized. Most were now in good condition, except one man who had to be resuscitated at the scene and remained in hospital, he said.
"The festival will continue as planned on Saturday. Cancellation ... was never an issue," Marek Lieberberg, who runs the festival, told fans on the event website.
He said the festival would continue to issue weather warnings via Facebook, Twitter and the event website.
Organizers warned fans more severe thunderstorms were expected.
The event website had reported early Saturday morning that at least 42 people were injured, eight seriously. But the numbers rose as more fans reported injuries in the early morning hours, according to a police spokesman.
Thirty-three people were injured at the festival last year by lightning strikes, according to German media.
Wenisch said the festival had been sold out for months