BEIJING — China's national observatory on July 17 renewed a yellow alert for high temperatures, as the country entered the second day of sanfu, the hottest time of the year that lasts about one month.

On July 18, parts of Zhejiang, Fujian, Jiangxi, Hunan, Guangdong, Hainan provinces, as well as Guangxi Zhuang and Xinjiang Uygur autonomous regions are expected to see temperatures as high as 37 to 39 degrees Celsius, the National Meteorological Center said.

In some parts of the above regions, temperatures may even hit 40 degrees Celsius, the center warned.

The center advised people to guard against the heat wave, and said workers exposed to high temperatures should take protective measures.

China has a four-tier, color-coded weather warning system, with red representing the most severe, followed by orange, yellow and blue.