Students have flocked to Dunedin's Hyde St Party after a slow start this morning, organisers say.
They believed the annual event was nearing capacity by the 1pm deadline, with room for 3600 people.
St John ambulance staff were on hand to make sure partygoers were OK, reports Otago Daily Times.
OUSA president Caitlin Barlow-Groom said it was a lot quieter this morning than it was at the same time last year.
"It's a bit colder than I thought it was going to be.
"I don't know if it's because of the weather or everyone's had a sleep in this morning, but by 1pm it's a one-way door policy, so everyone should be in by 1pm.''
Only about 500 students were in the street dancing at 10am.
It was a colourful affair, with people dressed as Teletubbies, sheriffs, convicts, angels, demons, zombies, gangsters, super heroes - one even dressed as a pregnant women from the 1980s.
Miss Barlow-Groom is herself a three-year veteran of the party. This year is her first behind the scenes, running the event, and it was much harder work, she said.
"It's fantastic to be behind the scenes. It takes a couple of months to organise. Everyone has been up since 5am getting everything set and the road's closed off until midday tomorrow," she said.
"Yesterday we put [rubbish] skips out, so they cleaned their flats out and cleaned the street out, and then tomorrow [Sunday] they'll get a nice early wake-up call from Campus Watch and residents will come out and clean the street. We get them to clean up their party.''
Miss Barlow-Groom said this year was OUSA's sixth year running the party.
"We've come so far. At the beginning I don't think we were quite sure of what we were actually taking on, and so now we've got this massive event.
"Last year we only had 10 arrests and no-one at the hospital, so it was a fantastic event, and I hope it's going to go the same this year.''
Students should wrap up warmly, as the day was likely to bring showers with hail and southwesterly winds in the afternoon, MetService says, and a high of just 12degC.