As the middle of October passes, residents in China's biggest metropolis are still wearing sleeveless shirts as if it was August.

And they are likely to continue sporting summer styles for the time being, with meteorologists forecasting that Shanghai's temperature will remain unusually high.

"This year's weather is really very unusual," said Shen Yu, senior expert at Shanghai Climate Centre. Normally autumn hits the city between the end of September and the beginning of October, but this year Shanghai has not yet entered the autumn season, Shen said.

Under meteorological criteria, autumn comes only after the average highest temperature falls below 22 C for five consecutive days. But for the past week, the city's average daily highest temperature has stood at about 28 C.

According to statistics, the average monthly temperature between June and August reached 28.7 C, the highest recorded since 1873, and a whole 2.7 degrees hotter than any other summer in the past 100 years.

Shanghai's temperature suddenly jumped when the summer season began on May 20. And though the western Pacific generated several typhoons this summer, none of them had an impact on the city. Cool weather at the beginning of September only held for three days, failing to end the scorching summer. The highest temperature recorded in Shanghai yesterday was 28 C.

Cao Xiaogang, the city's chief weather forecaster, explained that due to the strong influence of subtropical high-pressure, cold air from North China was unable to reach Shanghai.

Cao predicted that high temperatures will hold in Shanghai for the next two to three days with light showers likely on Thursday.

The delayed autumn seems to be becoming more common, with the duration of autumn shrinking more and more because of the ever-growing impact of global warming.

However experts believe that a sudden shift from summer to winter is not possible as the weather needs to go through a changing process.

In addition to the high temperature, the city's summer was also marked by limited rainfall and arid conditions. In August, Shanghai received only 27.8mm of rain 136.6mm less than the average for that time of year. September's rainfall of 86.1mm was 50 mm lower than the normal level.

Shanghai is not unique in encountering the unusual autumn. Meteorologists said unusually warm weather persisted throughout the country, with temperatures an average of 0.9 degrees higher.

Over the summer China recorded an average temperature of 21.4 C 1 degree higher than usual.

China Daily