Christchurch City Mission's night shelters are full and it is desperately short of blankets following this week's cold snap.
Freezing temperatures and the year's first sight of snow in the Port Hills had the Mission scrambling to get enough blankets to help those in need.
City Missioner Michael Gorman said the severerity of the cold snap caught everyone by surprise.
"We've had this wonderful summer and then even though we were warned the weather might get a bit rugged, we didn't quite expect it to get to the level it got," he said.
He said some people in need would go without blankets and warm clothes for a few days.
"But we'll get them as soon as possible, obviously. And if we have to buy them, well we'll have to blow the budget and buy them," he said.
"New Zealand, and Christchurch especially, has very cold snaps and with the housing situation the way it is, we have to really to make an effort to make sure people are warm."
The mission is appealing to the public to donate blankets or cash to help restock supplies. Items could be dropped off at the Christchurch City Mission on Hereford Street or at any Great Opportunity Shop around the city.
MetService said the worst of the cold snap was over and temperatures in Christchurch would gradually warm up.