Temperatures in China have plunged to their lowest in almost three decades, cold enough to freeze coastal waters and trap 1,000 ships in ice, official media said at the weekend. Since late November the country has shivered at an average of minus 3.8 degrees Celsius (25 degrees Fahrenheit), 1.3 degrees colder than the previous average, and the chilliest in 28 years, state news agency Xinhua said on Saturday, citing the China Meteorological Administration.