Unseasonably cold weather is causing chaos across the UK and forecasters are warning of more snow this weekend. Emergency services in the southwest launched a major operation overnight to rescue hundreds of drivers who had become stranded in heavy snow. Road and rail travel have been badly disrupted, schools have been shut, and planes at Luton and Bristol airports in southern England were grounded.To make matters worse, local authorities are concerned they are running out of gritting salt. “There are limits to the amount that we can get out of the ground because the producers can’t store it above ground either unless it is covered because it loses its salinity,” said Richard Kemp of the Local Government Association. “So we are working with producers. We are trying to source more stock.” The Midlands in central England have also been badly hit in what is being described as the UK’s coldest spell in two decades. The Met Office is forecasting further snowfalls into next week, with warnings for icy conditions across much of the country.