Police have seized more than a kilo of drugs and busted 159 people as the Splendour in the Grass music festival in northern NSW heads into its second day.

Revellers had been descending on the North Byron Bay parklands since Wednesday and police have been busy onsite with sniffer dogs and vehicle checks.

"In total over the three days, we have seized more than a kilo of drugs," a spokeswoman for NSW Police Media said today.

About half of the drug haul was cannabis, and the rest was ecstasy and yet-to-be examined powder.

However, crowds have generally been well behaved, the spokeswoman said.

"In general, it looks like everybody's behaving themselves. There were a couple of incidences, some antisocial behaviour and alcohol-related matters last night, but the vast majority of the crowd were well behaved," the spokeswoman said.

A total of 27,500 festival-goers are expected to attend each day with 17,500 of them camping on the site.

Proving the festival spirit was well and truly alive, revellers decked themselves in Woodstock-inspired garb, Indian headdresses and gum boots, though the footwear was not as necessary as it has been in previous wetter years.

The weather at North Byron has been unseasonably warm and dry, with temperatures reaching into the low 20s.

US hip-hop duo Outkast closed out the first night playing their first Australian gig with songs such as Ms Jackson and Hey Ya entertaining a packed Amphitheatre.

The Triple J Hottest 100 winner, Vance Joy, is set to play at the festival tonight while English pop star Lily Allen is expected to close the event tomorrow night.