More than 500 people are sleeping out overnight to raise awareness of homelessness.
Volunteers have already raised £89,000 by braving rain and cold temperatures inside the grounds of Cardiff Castle.
They have been joined by celebrities including Ruth Jones, Charlotte Church and Richard Parks, as well as musical acts on stage.
The event, hosted by charity Llamau, is part of a global campaign to end homelessness.
Ceris Jones has raised money but said raising awareness of the issue was just as important.
“It’s not just about charities helping those on the streets, there are lots who are living with friends, sofa-surfing or living in refuges who need help and support,” he said.
“It’s a real problem in Wales and it shouldn’t be happening on our streets.”
The global event in 50 cities is expected to attract about 50,000 people.
Half of the money raised is directly helping Llamau’s work in Wales.
Last year 7,5000 young people in Wales asked their local authority for help with homelessness, the charity said.
Jenna Lewis, Llamau director, said: “The problem has increased massively in recent years, both on our streets and the hidden homelessness of people living in places that aren’t safe.
“If we can help people sooner then we can help Wales become one of the first countries in the world to end homelessness.”