BEIJING: China will suffer the return of more heatwaves over the next 10 days, with high temperatures expected from east to west, meteorologists warned, with some cities issuing the highest level warning on Friday.

A sharp spike in temperatures is expected as soon as Saturday, before building up into heatwaves, defined as periods of atypically hot weather of three days or more. This Saturday is dubbed the day of the “big heat” in the Chinese Almanac, based on the traditional lunar calendar.

The hot spell is expected to be similar in scope as heatwaves from July 5-17, but more regions could be hit by temperatures of 40 degrees Celsius (104F) or higher, Fu Jiaolan, chief forecaster at the centre, told state media on Thursday.

Some cities in Zhejiang province, home to many of China’s factories and exporters, on Friday issued red alerts, the highest in a three-tier warning system, forecasting temperatures of at least 40 degrees C (104 F) in the next 24 hours.

The load on the national power grid is expected to reach a new high in summer, with safe operation expected to face “severe tests”, the Ministry of Emergency Management warned on Friday.

Zhejiang, as well as parts of Fujian, Guangdong, Hunan, Jiangxi and Chongqing, stand at risk of forest fires in the near term, the ministry also said.

The heat this summer has been described by Chinese weather watchers as extreme, boosting demand for air-conditioning by homes, offices and factories and pushing the load on power grids in more than a dozen provinces to records.

From June 1 to July 20, parts of the Yellow River and Yangtze River basins - major centres of industry and commerce - were hit by at least 10 high-temperature days more than the norm.

Since June, heatwaves have also scorched other parts of East Asia, Western Europe, North Africa and North America, sparking wildfires in many countries.

Scientists caution that climate change will only make heatwaves hotter and more frequent.

The highest-ever recorded temperature in China is a matter of debate.

According to Chinese media, the hottest period in the last 300 years was in July 1743 during the Qing dynasty, with a French missionary in Beijing said to have recorded an all-time high of 44.4C.

In 2015, a news portal in Xinjiang reported 50.3C at a weather station near Ayding, a dry lake in the Turpan Depression, one of the hottest places in China during summer.