Actress Natasha Little, who has recently appeared in the BBC adaptation of Wolf Hall, spoke to Premier from Serbia where she's been helping to distribute supplies.
"We're just beginning the winter here and it is zero degrees. They are expecting temperatures to drop to minus 20. There's a particularly severe wind here, which will make it feel really, really cold.
"Unless there's proper provision there will be sickness and death."
Mrs Little has also spoken of a new generation, whose life in the camps is the only one they know.
"There are tiny babies who have been born into a refugee situation. They don't have nappies, or appropriate clothing.
"I saw children without shoes, without socks. One child did have shoes but she hadn't been wearing socks and her feet looked in a terrible mess. There were children in very thin tops with no coats."
In November, some 140,000 migrants and refugees made the dangerous journey to Europe across the Mediterranean Sea, marking a 36.5% drop from October, when a record 220,535 arrived on Europe's shores, the UN refugee agency (UNHCR) said.
Mrs Little is urging believers in the UK to send the refugees a 'priceless gift' this Christmas.
"When I saw them I just thought: 'Gosh, even Jesus had a manger, and for these people this is perhaps a little manger for them in a long journey where they've had very, very little.'"
She suggests holding collections at carol services or giving charity donations as presents this year, as ways to raise support.