Heavy fog enveloped Beijing and other north China provinces Thursday, causing flight delays and highway closures.

Visibility in southern Beijing was below 1,000 meters in the early morning, forcing the closure of the Beijing-Shijiazhuang highway.

Dozens of flights into and out of Beijing were delayed in the morning, according to the website of the Beijing Capital International Airport.

The haze had faded by noon, but a cold front is forecast to disperse it completely Friday, according to the Beijing Meteorological Bureau.

The fog became thicker early Thursday in the northern port city of Tianjin, reducing visibility in Xiqing District to as low as 20 meters and that in Jinghai County to 30 meters.

Six of the 12 highways through Tianjin had been closed by 9:30 a.m..

Lingering fog has reduced visibility in Tianjin to less than 1,000 meters for three straight days.

Visibility in parts of northeastern Liaoning province was below 200 meters, leaving at least four highways closed.