BEIJING -- China's meteorologists issued a yellow alert on Saturday for high temperatures, the second in a four-tier warning system, with some southern provinces expected to see temperatures of up to 40 degrees Celsius.

The heat wave led to historic highs temperatures in some areas in July, and will continue to bake southern and central China on Saturday, the National Meteorological Center said.

The observatory expects some regions in Sichuan, Chongqing, Guizhou and Xinjiang to see temperatures above 35 degrees Celsius.

Temperatures in downtown Chongqing, and parts of Shaanxi, Henan, Hubei and the southeastern provinces could rise to 39 degrees Celsius, it said.

The public was reminded to pay attention to the weather and take precautions in outdoor activities. Authorities are closely watching the power supply to avoid accidents.

Heat waves have hit most of the country's southeast over the past month. Shanghai, for example, recorded a temperature of 40.9 degrees Celsius on July 21, the highest on record in the city in 145 years. The extreme hot weather has increased the number of people suffering from heatstroke.

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