Festival-goers were due to start trickling in as early as Monday and Tuesday, but organizers then urged people to stay at home and wait for better weather.
The area was nevertheless filled with people and on Wednesday morning the festival announced that the maximum number of visitors had been reached, given the weather conditions.
The festival has sold tickets to 85,000 people. On Tuesday evening, co-founder Thomas Jensen said they had no choice but to close the area to more people, for safety reasons.
More than 200 concerts are planned for the festival, including Iron Maiden and Megadeth.