A cold front will sweep across most parts of north and northeast China during the next three days, the National Meteorological Center forecast on Monday. Many regions in northeastern and northern provinces can expect strong gales and a plunge in temperatures of 4-8 degrees Celsius on Monday and Tuesday, the observatory said. Usagi, this year\'s most powerful typhoon to hit China, was downgraded to a tropical storm after making landfall in southern Guangdong Province Sunday evening, the center said. However, Usagi would bring heavy rain to Guizhou, Guangdong, Yunnan provinces and Guangxi Zhuang Autonomous Region as it continued to move northwestward in the coming three days. At least 25 people have been killed in Guangdong as Usagi came ashore Sunday evening.