Royal Mail has said it will be delivering 14,000 items to around two million homes with evening deliveries for the last four days before Christmas Eve.
Royal Mail said that the authorities are currently doing "all they can" to keep open major roads but that despite this some "major routes" have been "significantly impacted" by the recent snow.
Mark Higson, Managing Director of Royal Mail, said, "We are planning up to a total of 14,000 - weather permitting - additional delivery rounds on Monday, Tuesday, Wednesday and Thursday evening.
"We have had postmen and women on the streets for the last two Sundays in a row. Royal Mail is committed to doing everything possible to deliver letters, cards and parcels on behalf of its customers."