Beijing :China's meteorological authority has issued a blue alert, the lowest level in a four-tier warning system, for rainstorms in southern parts of the country, the media reported on Sunday. Until March 27, rainstorms from 180 to 250 mm will pelt parts of Hunan, Guizhou, Guangxi and Guangdong provinces, the National Meteorological Centre (NMC) said in a statement. Xinjiang and Qinghai will receive snow or sleet until Sunday, the NMC said. China has a four-tier color-coded warning system for severe weather, with red being the most serious, followed by orange, yellow and blue. The NMC also maintained yellow alert for smog on Saturday as the pollution, which has choked most regions in the north, showed little sign of abating.