BEIJING, July 25 (Xinhua) -- China's national observatory Saturday renewed a yellow alert for high temperatures, as a heat wave has engulfed most parts of the country.

On Saturday, parts of Hunan, Guangdong, Guangxi, Hainan, Liaoning, Hebei and Xinjiang are expected to see temperatures above 35 degrees Celsius, the National Meteorological Center said.

In some of these regions, temperatures may reach as high as 37 to 39 degrees Celsius, or even hit over 40 degrees Celsius, the center said.

The center 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.