This year's second red heatwave alert was issued yesterday, with the mercury hitting 40.2 degrees Celsius in downtown Shanghai.
Yesterday was the seventh consecutive "scorching day" — days over 37 degrees — during this summer's heatwave that so far has lasted a total of 18 days, with temperatures over 35.
The temperature hit a historic high of 40.9 degrees on Friday.
Since 1873, the Xujiahui observatory station has reported 13 days with temperatures higher than 40 degrees.
The second-highest reading was recorded at 40.8 degrees in 2013, the hottest year on record.
The summer of 2013 had 47 days above 35. There were 24 "scorching days," including a record 10-day consecutive period.
That record is likely to be equaled or broken as temperatures are forecast to remain higher than 37 degrees until Thursday.
Today, the city will hit 40 again. Tomorrow's high is forecast at 38 and temperatures are then expected to drop a degree each day.
But the mercury is forecast to stay around 35 degrees over the weekend.
As the heatwave intensified, power is in hot demand as residents crank up air conditioners to escape the scorching heat.
Electricity demand yesterday broke the record set just last Friday. By 12:25pm yesterday, the demand topped about 32.52 million kilowatts.
Hospitals are also busy these days.
The exposure to the scorching sun increases risks of being burnt. The Ruijin Hospital is receiving more than 500 sunburn patients a day, nearly twice as much as average.
"Usually, we close at 4:40pm but these days there are too many patients so doctors have to work until 7pm," said nurse Zhou Jie. "Nearly one third of the patients are babies."
Doctor Huan Jingning said infants aged around two account for many of the patients.
"They can walk and talk, but they can't recognize risks. If parents are careless, they will be left in danger," the doctor said.
"Some are burnt by hot water and some are injured when they walk barefoot under the sun."
Usually, residents are more worried about PM 2.5 pollution, but this summer the enemy has changed. This month, Shanghai has had 15 days of ozone air pollution. It doesn't cause choking gray skies, but it is harmful.
Yesterday, the Air Quality Index reached 161 — the fifth consecutive day of moderate ozone pollution. It will continue to Thursday, the environmental protection authority said.
After long exposure to sunshine, volatile organic compounds and nitrogen oxides, generated from coal-burning, vehicle exhaust and factory processing, undergo photochemical reactions and create an excessive amount of ozone.
High levels irritate the respiratory system, damage lung functions and even cause deaths. Residents are advised to stay indoors.