China's national observatory on Sunday renewed its yellow alert for a vast region across the country, where temperatures above 35 degrees Celsius are predicted for daytime.China has a four-tier warning system for severe weather, with red being the most serious, followed by orange, yellow and blue, Xinhua news agency reported.During the daytime on Sunday, high temperatures above 35 degrees Celsius are expected to scorch regions to the south of the Yangtze river and the central and southern parts of north China, the National Meteorological Centre said.Parts of Guangdong, Jiangxi, and Fujian will see temperatures up to 39 degrees Celsius.Rain storms are forecast in the middle and lower reaches of the Yangtze river from Sunday night to Monday.Heavy rains will hit parts of Chongqing, Guizhou, Hunan, Hubei, Anhui, Jiangsu, Jiangxi and Zhejiang.Geological disaster risks are high in parts of Sichuan, Chongqing, Yunnan, Anhui, Jiangxi and Zhejiang, the centre warned.