Shanghai's sky darkened and temperatures cooled yesterday afternoon as a thunderstorm swept through the city, dropping hailstones in the south, affecting dozens of flights and flooding households and streets.

A construction worker was killed in the storm. The middle-aged migrant worker was shocked while decorating a primary school, witnesses said. It was unclear whether he was hit by lightning or a more immediate form of electricity.

The accident occurred at the Yinghuayuan Primary School at 28 Guiping Access Road while lightning and thunder dominated the sky, witnesses said. The unidentified man was sent to the Shanghai No.6 People's Hospital, where he was pronounced dead.

During the storm, the temperature dropped to 24.5 degrees Celsius, the Shanghai Meteorological Bureau said. The morning had been as hot as 35.3 degrees, making yesterday the 28th high-temperature day this year.

The bureau said similar weather - sunny and cloudy with thundershowers - will continue until next week.

The high temperatures for the rest of this week are expected to be around 34 degrees, the bureau said.

Meanwhile, officials said the weather this summer was abnormal, with several heat records set. The average temperature in August so far has reached 32.2 degrees, a historic high. Four consecutive days with the maximum high over 39 degrees are also a city record.

Yesterday's rainfall started about 2pm and mainly concentrated in Minhang, Yangpu and Huangpu districts and the Pudong New Area. The precipitation reached a high of 90 millimeters, in Minhang, said the city's flood control headquarters.

About 10 streets in Yangpu were flooded, where the precipitation was the second highest in the city, the headquarters said.

At least 15 households in Lane 60 Weinan Road were flooded. The heaviest flooding was reported in a staff dormitory on Jiangdong Road in Pudong, where the water measured 40 centimeters deep.

Authority of the city's Hongqiao Airport said at least 10 flights were forced to land in the Pudong International Airport and Hangzhou, Zhejiang Province, because of the storm. Another five flights were canceled with 10 delayed in the storm. At Pudong International, 96 flights were delayed and two were canceled.

Hail with a diameter of 9 millimeters appeared in Minhang, said the weather bureau. The hail did not last long and no one was reported injured.

"The thunderstorm and hail were caused by a strong cloud mass, which developed very fast and generated unstable energy," said Li Jinyu, a chief service officer of the bureau.