The World Health Organisation's regional director says people in the UK should either postpone large Christmas gatherings, or have their family dinner as a picnic in a park.
Dr Hans Kluge, WHO regional director for Europe, has urged people to avoid large gatherings indoors at Christmas.
He said: "If it's a large gathering of vulnerable people, you may postpone that gathering until you can safely gather.
"Despite the cold, if local restrictions permit, gather outside with loved ones for picnics in the park."
Dr Kluge said many other religious festivals, including the Islamic holy month of Ramadan and the Hindu festival Diwali, had been marked with virtual gatherings and "distance celebrations", reports The Mirror.
Last year, temperatures plunged to -3C in parts of the UK on Christmas morning.
Andrew Hayward, professor of infectious disease epidemiology at University College London and a member of the Scientific Advisory Group for Emergencies, warned that mixing at Christmas poses "substantial risks", particularly for older people.
He said there had been "far too much emphasis" on having a normal festive period.
Professor Hayward added that the country was "on the cusp" of being able to vaccinate older populations and it would be "tragic" to throw away the gains made in suppressing coronavirus.
The Government is reportedly considering plans to ease restrictions on indoor socialising for five days from December 24.
In return, a tighter lockdown may have to be enforced to stop hospitals from being overloaded by the uptick in infections.
Downing Street said plans for Christmas would be set out next week.
