Lollapalooza music festival was halted on Saturday as Chicago was hit by a powerful thunderstorm.
Tens of thousands of concert-goers took shelter in parking garages that had been designated evacuation centres for the sold-out three-day event.
Crowds were let back into the Chicago lakefront venue three hours later after the worst of the storm had passed.
An extended curfew allowed Red Hot Chili Peppers, Saturday’s headline act, to perform as scheduled.
Australian band the Temper Trap and US rock group Alabama Shakes were among the acts whose sets were cancelled due to the interruption.
According to a statement on the Lollapalooza website, organizers “made the decision to evacuate Grant Park [at 15:30 CST] in response to warnings from the National Weather Service”.
“In all, more than 60,000 festival-goers and nearly 3,000 staff, artists and vendors were safely evacuated in 38 minutes.”
“We want to thank the tens of thousands of festival-goers, staff and artists who calmly and safely exited,” said a spokesperson for Lollapalooza promoter C3 Presents.
Jack White, Sweden’s Miike Snow and Britain’s Florence and the Machine are among the acts scheduled to perform on Sunday as this year’s festival draws to a close.
Organizers announced on Saturday that a Lollapalooza festival would be held in Tel Aviv, Israel in August 2013.
Versions of the event will also take place next year in Sao Paulo, Brazil, in March and Santiago, Chile, in April.