About 200 people will sleep rough in the Octagon tonight to raise funds for the Dunedin Night Shelter.
The shelter has 12 beds, and last year provided a total of 648 beds to homeless people, but said funding problems had left it in a state of flux.
The shelter is trying to raise $220,000 to purchase the property they currently occupy, the sleep out event will contribute toward this, along side many other fundraising initiatives.
Dunedin Night Shelter Trust chair David Brown said the shelter's current level of support was proving increasingly hard to sustain.
"What we want is some permanence for the night shelter, because it's very difficult to move a night shelter," he said.
"We're renting these buildings at the moment and they're ideal for what we do now, and they're ideal for what we can do now into the future."
Tonight's Sleepout 2015 is organised by 'UniCrew', a group of volunteer students at the Student Volunteer Centre at the University of Otago.
At least three politicians will be among those braving the outdoors: Dunedin City Councillor Aaron Hawkins, Dunedin North MP David Clark and Green Party co-leader Metiria Turei.
The Dunedin Night Shelter receives just $20,000 a year from the Dunedin City Council and, last year, was given a one-off $200,000 grant from the Community Trust of Otago.