Shanghai's air will clear up somewhat Thursday after heavy pollution descended on the city during the Dragon Boat Festival holiday Wednesday.

A change in the wind's direction will help blow the pollution somewhere else, according to Fu Yi, a press officer from the Shanghai Meteorological Bureau.

"Eastern winds from the sea will take the place of the winds out of the north tonight, which will ease the air pollution in the city," Fu told the Global Times Wednesday afternoon.

Shanghai's Air Quality Index (AQI) breached the 200 level in the morning, indicating heavy pollution, according to data from the Shanghai Environmental Monitoring Center. The AQI peaked at 218 around 4 pm, with PM 2.5 as the primary pollutant driving up the index.

The 24-hour average concentration of PM 2.5, or particulate matter less than 2.5 microns in diameter, reached 158.6 micrograms per cubic meter.

The monitoring center advised on its microblog Wednesday that children, the elderly and residents with heart and lung conditions ought to stay indoors. It also suggested that all residents limit outdoor activities for the day.

The monitoring center's chief forecaster, Duan Yusen, denied Wednesday that the air pollution in Shanghai had much to do with the straw burning in the fields of Anhui Province that caused the severe haze in Nanjing, Jiangsu Province Monday night, according to a news report on Shanghai Television Station.

"Straw burning will cause an increase in potassium in the air," Duan said. "However, although there was such an increase, a large proportion of the air pollution came from industrial and motor vehicle emissions."

The day of heavy pollution followed 10 straight days of good or moderate air quality, from June 1 to June 10, according to data from the monitoring center.

It will remain cloudy in Shanghai until Sunday with a good chance of passing rain showers across the city, according to the weather bureau. The temperature is expected to rise gradually and reach a high of 28 C this weekend.