Pedestrians do their best to cope with the heat on Nanjing Road E. yesterday.(Zhu Weihui)
The mercury reached 40.3 degrees Celsius yesterday, making it the hottest day this year and the third-hottest since the city began keeping records in 1873, said officials.
The Shanghai Meteorological Bureau issued an orange heat wave alert at 9:17am yesterday morning and upgraded it to red — the highest in a three-level color system — at 1:12pm to warn that the mercury would hit 40 degrees. It was this year's second red heat wave alert — the first was last Saturday, when the mercury hit 40 degrees.
According to the weather bureau, the hottest day in history was on August 7, 2013 (40.8 degrees Celsius). The second-highest temperature was 40.6 degrees, which occurred three times in July and August 2013. The fourth was a 40.2-degree high on July 12, 1934 and again on August 8, 2013.
Fu Yi, an official at the weather bureau, told Shanghai Daily that the record-breaking temperatures are mainly caused by direct sunlight and sinking air brought by the subtropical high-pressure belt.
"The subtropical high brings us sunny weather and the strong sunshine makes the ground overheated. Meanwhile, the sinking air's compression also contributes to the rising temperature."
Fu said the southwesterly wind blowing through the city yesterday was too warm to alleviate the scorching conditions.
The city yesterday entered "Zhong Fu" — the hottest period during "San Fu," which is also known as the dog days of summer. This year's "San Fu" will last for 40 days, 20 of which comprise the "Zhong Fu" period.
Along with the heat, afternoon thundershowers are expected through the end of July.
A mixture of sun and clouds is expected tomorrow with a high of 39 degrees, but the mercury will gradually fall to 35 degrees by the beginning of next week.
The sweltering weather is likely to subside next week after the subtropical high moves a bit northwards and cool southeasterly air flows into the city.
Meanwhile, electricity usage in Shanghai reached a record high of 31,196 megawatts yesterday afternoon, the State Grid Shanghai Electric Power Company said. The city's power usage, which is up 4.6 percent over last year, hit the historic peak at 1:35pm.
The power supplier said the city can generate as much as 20,000 megawatts of electricity, but about 15,012 megawatts can be supplied from sources outside the city if it is needed.
The power supply is still sufficient to keep the city running, a company official said.
Over 2,000 repairmen and 400 vehicles are standing by to deal with any power problems, the company said.
Repairmen are dealing with about 1,900 power malfunctions every day on average this summer, it added.
