Severe fog in Shanghai brought air, sea and rail transport to a standstill for a second day Wednesday, with some 900 flights and nearly 100 ships affected by the conditions, which were expected to improve Thursday.

Shanghai's continuous rain over the past three days worsened foggy conditions in the city's eastern pocket for a second day Wednesday, causing headaches for authorities.

Shanghai Pudong International Airport had cancelled 298 departures, diverted 150 flights to other airports and experienced 440 delays by 3 pm Wednesday.

"This is the worst fog we've seen at the Pudong airport since operations began here in 1999," Tian Lu, a press officer for Shanghai Airport Authority, told the Global Times Wednesday.

Nearly 20 overseas flights were rerouted to Hongqiao International Airport Wednesday as the airport, situated in the city's west end, was not affected by the heavy fog.

The low visibility Wednesday also prompted two local carriers to cancel domestic flights between 4 pm and 8 pm as a safety precaution.

The city's Yangshan Deep-Water Port remained closed for a second consecutive day, grinding 97 ships to a halt while ferries to Chongming Island were prevented from traveling past Wusong and Baoyang ports Wednesday afternoon.

On the tracks, three high-speed trains bound for the capital were unable to leave Shanghai due to the fog Wednesday, while another dozen incoming trains were delayed from entering the city.

A cold air pressure system from North China moving southwards was Wednesday predicted to help clear most of the heavy fog Thursday, according to weather forecasters, said Fu Yi, chief service officer for the city's meteorological bureau.