BEIJING —?China's national observatory issued a yellow alert on Friday for high temperatures, the least serious in a three-tier warning system, with some northern provinces expected to see temperatures of up to 39 degrees Celsius.

The heat wave, which has swept across northern provinces and led temperatures in some areas to historic highs in May, will continue to bake North and Northeast China on Friday, the National Meteorological Center said.

The observatory expected some regions in Inner Mongolia autonomous region to see temperatures above 35 C, and temperatures in some parts of Liaoning and Hebei provinces could rise to 39 C, it said.

It noted the heat wave will gradually ease starting Saturday.

In the coming three days, coastal regions in the Guangxi Zhuang autonomous region, Hainan and Guangdong provinces will be hit by heavy rain or downpours, the observatory forecast.