Scorching heat has persisted in northern and eastern parts of China since Monday, driving up the number of emergency calls and sending hundreds of people to hospital with heat-related illness.
Beijing, Shanghai and Chongqing as well as cities in Hebei, Henan, Shandong and Jiangxi provinces have issued heat wave warnings, with temperatures soaring to 40 C in many areas on Wednesday.
"The heat wave is expected to move toward the south, with rainfall coming around Friday in the north, cooling down the hot weather," said He Lifu, chief forecaster of the National Meteorological Center.
"Children, the elderly and the infirm are advised to stay indoors due to the soaring temperatures," He said.
Beijing issued this year's first heat wave alert on Tuesday with the temperature soaring to 36 C on Wednesday.
In the capital, ambulance calls surged to about 6,000 times the average every day since Monday.
"Patients with heat-related illnesses surged 23 percent in the first three days of July, compared with early June," said Guan Na from the Beijing Emergency Medical Center.