The public is being urged to alert anyone sleeping rough to homeless charities, as temperatures are set to dip below freezing this week.
It comes as the latest figures from the Department of Housing show almost 15,000 people will spend Christmas without a home.
Frost and lows of -3 degrees are expected across the country on Monday night.
Interim executive director of the Simon Communities of Ireland, Tony Geoghegan, said sometimes people do not know how they can help.
"They might want to help, but are afraid or just don't know what to do. So we recommend in those cases, that they ring their local homeless service," he said.
"Make contact, and say: 'Look, I saw this person sleeping here.' And don't assume that someone else knows or someone else will do it because unfortunately when temperatures drop, people can die. It has happened."
