The heaviest rain of this year hit Shanghai on Thursday, prompting weather officials to issue a red rainstorm alert for only the second time.

The World Expo site in Pudong New Area had the most rainfall of 12.9 centimeters up to 4:00 PM.

Seven districts recorded rain of more than 10 centimeters, the Shanghai Meteorological Bureau said.

The bureau issued an orange rainstorm alert at 11am and upgraded it to red, the highest of three levels, at 12:48pm.

Both the weather bureau and fire brigade workers were on water-clearing duties, officials said.

"It is the first red alert since a storm two years ago," said Chen Min, a forecaster with the bureau.

The rain stopped later in the afternoon and rainbows were a stunning backdrop to sunset.

"The storm was caused by a strong rain-cloud cluster moving east from the west," Chen said.

Forecasters said thunderstorms or rain would continue until at least tomorrow.

The maximum temperature would rise to 32 degrees Celsius today from yesterday's 29 degrees, said Chen.

Shanghai Normal University, which is located in one of the areas hardest hit by rain, suffered extensive flooding in the afternoon.

"It was hard to walk on campus ... the water was over my ankles," said Xu Yuan, a graduate student who is living on campus during the summer vacation. "The campus was like a swampland."

Tian Ye, an employee of a research institute on campus, echoed Xu's sentiments. "The water was about 10 to 15 centimeters deep on the first floor of our building," Tian said.

Dormitories on the first floor were also flooded but most students are on vacation.

More than 3,000 homes in Luwan, Huangpu, Zhabei and Jinshan districts were flooded to a depth of 5 to 10 centimeters.

Water, between 10 and 30 centimeters deep, also flooded more than 70 roads across seven districts, according to Shanghai Flood Control Headquarters.

"The rain was far beyond the city's draining ability," said Zhang Zhenyu, an official with the headquarters.

Excess water was cleared up by last night.

In Songjiang District, the roof of a residential house collapsed, leading to at least one lucky escape. "A piece of roof fell onto a passer-by's umbrella and bounced off," said a witness.

(Shanghai Daily July 31, 2009)