Smog will return to Beijing during the weekend ahead, although it had been dispersed by cold wind on Saturday evening, the municipal meteorological authority said.

Citizens have enjoyed good air quality on Sunday after widespread smog affected a large part of North China over the past several days, with air conditions in northern cities such as Beijing and Tianjin severe.

However, the capital city will again suffer from increased smog starting Friday, though it might not last long or be as severe as last week, said Zhang Yingming, senior engineer at the city's meteorological department.

Netizens have questioned why the bright sky failed to last more than three days. In answer, Zhang said Beijing weather has always followed a cyclical pattern. Changes are more obvious nowadays, with the effect of increasing emissions, he added.

Experts said it is not rare to witness smog during October, as it had happened in previous years, citing climatic data. Beijing easily falls victim to smog in the latter half of a year, due to its geographic location.

The Beijing Meteorological Observatory issued a yellow alert for smog last Wednesday. Air pollution is a thorny problem for the government ahead of the Asia-Pacific Economic Cooperation Economic Meeting slated for November.

The environmental watchdog in north China's Henan province has attributed lingering smog to burning fields of straw. It said pollution discharged from the 7,893 burning sites it monitored over the National Day holiday period had accumulated in the air, which lacked flow.