DOVER, Del. (WPVI) -- The 2015 Firefly Music Festival is officially under way and first bands have taken the stage.
The 4 day music festival is taking place near Dover International Speedway in Delaware.
Many began camping out Wednesday night, enduring the rain but still having a good time.
"I've never camped out at an event before. I think that makes, that there are so many days, so many cool people here - that's what makes it so much fun," said Jullia Reger from Springfield, Pennsylvania.
Sir Paul McCartney is tonight's headliner. Other headliners scheduled to perform this weekend include Snoop Dogg, Kings of Leon, The Killers and Hozier.
For the first time ever, the festival is sold out.
This year, Firefly did not offer single day passes and concert-goers could only purchase 4 day passes.
Organizers expect some 90,000 people to attend and watch dozens of bands on more than half a dozen stages.
"Its nice because each stage has its own sound space so you don't have overlap with each set," said Anjuli Bhadurhauck from Street, Maryland
The music is on all weekend, rain or shine.
The festival wraps up Sunday at midnight.
Organziers and festival goers say there have been few problems and it seems most people are just having a great time.