More than 50,000 revellers are expected to watch as One Direction, Calvin Harris and Coldplay kick off the Glasgow Green extravaganza.
Partygoers who arrived in the city for Radio 1's Big Weekend refused to have their spirits dampened by the predicted rain showers.
Despite clear skies this afternoon, showers are expected to move in tonight.
Temperatures are set to reach a peak of 16ºC this weekend.
The giant outdoor party will see dozens of big names stars including Katy Perry, Paolo Nutini and Example perform today and tomorrow.
Last night, a crowd of 14,000 over-18s were entertained by a packed bill of top DJs, including some of the best known names from the dance music world.
Tiesto and Pete Tong performed alongside Radio 1 DJs Annie Mac, Zane Lowe and Danny Howard in George Square.
The whole event was broadcast live on Radio 1.
One Direction will start the party this afternoon before Coldplay bring the packed line-up to a climax at around 11pm.
A total of 50,000 passes for the main event sold out in just 30 minutes.
Jason Carter, Radio 1's head of live music, events and popular music, said organisers always expected there would be a high demand.
He said: "The event's reputation is such that every year ticket demand is huge, we are not surprised that tickets have gone so quickly."
Organisers are warning partygoers that the over-18s age restriction will be strictly adhered to and people must bring identification with them.
Food and drink can not be brought into Glasgow Green, with the exception of water in a bottle with an unbroken seal.
There will also be food stalls on site.
Glasgow Green has been enclosed with fencing ahead of today's musical spectacular to allow tents, stages and bars to be set up.
Council bosses urged people to plan their journeys in advance to avoid gridlock.
Motorists will be banned from streets around Glasgow Green from 1am today until just before midnight tomorrow.
A council spokesman said: "Diversions will be signposted on streets around the events.
"Drivers are advised to consider alternative routes before and during these events."