China's weather authorities on Saturday issued a blue alert, the lowest level in its four-tier warning system, for heavy rains in the southern region in the next 24 hours.From 8.00 a.m. Saturday to Sunday, heavy rains and storm are expected in many southern provinces, including Guangdong, Hainan, Fujian and Yunnan, the National Meteorological Centre (NMC) announced.Some parts of the above-mentioned provinces are going to see torrential rain of 100 to 130 mm within 24 hours, Xinhua news agency reported.The NMC warned local governments to take emergency measures against storms, cut off outdoor power supply in dangerous regions and prevent potential disasters, including mountain floods and landslides.China has a four-tier colour-coded weather warning system, with red representing the most severe warning, followed by orange, yellow and blue.