The rest of this week is expected to be warmer under a weak high pressure with temperatures surging to 27 degrees Celsius on Thursday, forecasters said.

The high will remain at or above 25 degrees on Friday and Saturday until cold air from the north will see a drop to 22 degrees.

Shanghai Meteorological Bureau said the sky will be clear on Thursday with weak winds and high humidity. Some areas are likely to see fog.

Since Sunday there have been four days with an average temperature below 22 degrees. One more day would mean that autumn had arrived. However, Thursday's expected high temperature will delay the official announcement.

After a mild Friday, another round of cold air will arrive late on Saturday. The impact of the cold air will continue into early next week, with the sky mainly cloudy to overcast.

Meanwhile, the city’s disease prevention and control authority has prepared flu vaccines which will be ready in all districts before the end of the month.

Children between 6 months and 5 years old, people aged 60 or over, chronic disease patients, medical staff, family members and babysitters of infants younger than 6 months old and women who plan to get pregnant during flu season are a priority.