Royal Mail has said that it has invested £20 million to deal with what it called "the most severe weather in 30 years", with extra resources being diverted to the North East, the Midlands and Scotland.
Around 3,000 extra people will be recruited for the next two weeks to support its Christmas operations, while another 500 HGV drivers and 250 large lorries have been taken on for the Christmas period.
The news comes on what Royal Mail called its busiest day of the year, with 130 million cards, letters and packages being processed just today.
Mark Higson, Managing Director of Royal Mail, said, "We are pulling out all the stops to deliver this Christmas. The worst December weather the UK has seen in almost 30 years has had an impact on our services to some parts of the country. With this additional £20m investment, we are committed to ensure we deliver letters and packets as quickly as possible.
"Our people are doing a great job in very challenging conditions. I would like to thank them for their tremendous efforts to ensure we continue to deliver right up until Christmas Eve."