Online shoppers could face a Christmas Day without turkey and many gifts after snow crippled some postal deliveries
Royal Mail said it was doing "everything possible" to ensure the post arrived on time.
But it said the "severe weather" had made certain roads impassable.
Supermarket chains Asda, Tesco and Sainsbury's said they had been forced to cancel some home deliveries because of the treacherous conditions.
Many people who shopped online to avoid high street crowds and take advantage of low prices now face an anxious wait to see if their goods arrive.
Maggie Atkins, 73, from Overton, Hampshire, told the Daily Mail she had yet to receive her delivery.
"I was told my order was cancelled because of the weather," said Mrs Atkins, who takes morphine to cope with pain caused by osteoarthritis.
"I live alone and I can't even hobble around a supermarket. I really think Tesco could have offered a priority service to the disabled."
Despite the adverse weather, online retailer Amazon said goods ordered before 2pm today should arrive before December 25.
"There may be a short delay to the arrival of some deliveries in the worst affected areas but all of these deliveries are expected to be made before Christmas," said a spokesman.
Asda said a "small number" of online customers had been affected.
Tanya Lawler, Sainsbury's director of online, said: "Disruption to service has affected less than 1% of our orders in the past week, and we've been offering alternative delivery times where possible."
A Tesco spokesman said: "It goes without saying that grocery deliveries in some areas have been impacted by the weather and treacherous driving conditions. Nonetheless, all of our drivers are facing these challenges head on and we have now increased capacity to try and make sure that nobody is left disappointed."
Royal Mail said the majority of deliveries would arrive by Christmas.
"More than 95% of Royal Mail's operation is working completely normally and we expect virtually all of the seasonal postbag of more than 100 million a day to be delivered by Christmas but in a very small number of areas some deliveries have been disrupted because of severe weather and bad road conditions," said a spokesman.
"Our people are out on delivery in often appalling weather conditions to keep the mail moving and we are totally focused on doing everything we possibly can to deliver all customers' letters and parcels posted in our network by the latest recommended posting dates by Christmas."Reuse content