Some of the worst snowfall in 25 years has hit the United Kingdom. Heathrow Airport has been shut down to clear runways, but the airport says that once reopened, flights are still expected to be canceled or delayed. Northern Ireland transportation authorities are warning holiday shoppers and travelers not to tread outside, since slush from a remaining storm has frozen over. In Wales, several medical workers are unable to reach the hospitals due to poor road conditions. Bus services are down as well as several railroad lines throughout the U.K. The snowy conditions have also affected parcel services—some companies have warned that a backlog of deliveries means that some packages won't reach their recipients until after Christmas. Throughout Europe, winter weather has affected travel conditions. In Germany, 2,500 passengers were stranded overnight at Frankfurt Airport, and Italy reported hundreds of cars stranded on the local highways.