Extreme weather caused the Shanghai's weather bureau to issue alerts yesterday for heat, wind, rain and thunder for the first time in one day this year.

A yellow rain and thunder alert was issued as a thunderstorm dumped buckets of rain on the city yesterday afternoon.

Rainfall of 53 millimeters per hour was recorded in Luwan District and some homes there were flooded, according to the city's flood control headquarters.

The most rainfall was in Pudong New Area. It was measured at 63 millimeters per hour.

The temperature climbed to 35.8 degrees Celsius yesterday, causing the weather bureau to issue a yellow heat alert, the lowest in a three-level system, around noon.

Yesterday was the 17th day with the mercury above 35 degrees Celsius this summer.

A blue wind alert was also issued yesterday.

"Strong winds occurred in some areas of the city and peaked at 72 kilometers per hour in Jiading District," the bureau said yesterday in a statement.

However, the weather is expected to improve this weekend. Chen Min, chief service officer of the bureau, said it will be cooler and drier this weekend.

It will be mostly cloudy with some light rain and temperatures will range between 26 and 34 degrees, according to the bureau.

Meanwhile, this week's heat wave has resulted in a rise in patients at the city's hospitals and increased demand for ambulances.

The Shanghai Medical Emergency Center said ambulances responded to 5,000 calls from August 13 to Wednesday.

The emergency center responded to 808 calls alone on Tuesday, the most in one day in recent years.

(Shanghai Daily August 21, 2009)