The family of a North Yorkshire man who went missing after a night out in Newcastle say they are becoming increasingly concerned for his safety.
Duncan Gibbon, 21, from Northallerton, was in the city celebrating a friend's 21st birthday on Saturday.
The last known sighting of Mr Gibbon was in Fever Bar at about midnight.
Mr Gibbon's mother Kate said she feared for the safety of her son if he was exposed to sub-zero temperatures for any length of time.
Police have described the disappearance as out of character and have appealed for anyone with information about his whereabouts to come forward.
'Very, very cold'
Mr Gibbon is described as white, of slim to medium build and 5ft 10in tall.
He has short straight brown hair, is clean-shaven, with a fresh complexion and blue eyes.
He was wearing blue denim jeans, a turquoise coloured T-shirt with black on the top and shoulders and a grey jacket.
Mrs Gibbon, who travelled to Tyneside to assist police, said: "It has been a very, very cold day and night and it's really frightening because you just can't survive outside in this kind of weather.
"So naturally we are very worried about his wellbeing and his safety.
"It would be the best Christmas present ever to just know that he is safe."
Temporary Supt Geoff Logan, of Northumbria Police, said: "We are concerned for his welfare due to the length of time he has been missing and the cold weather conditions.
"It is imperative that anyone who saw him on Saturday night or has seen him since contacts us as soon as possible."