Pakistani commuters travel during a cold and foggy morning in Islamabad on Jan. 8. Ongoing foggy weather in Punjab and other parts of the country has badly affected flight and rail schedules.

A Pakistani vendor adjusts sugarcane while waiting for customers in the foggy morning in Islamabad, Pakistan on Jan. 8.

Pakistani people travel along the road during a foggy morning in Islamabad on Jan. 8. The fog has also disrupted flight schedules at the Islamabad airport and four Islamabad-bound flights from Dubai and Afghanistan were diverted to Lahore.

A horse looks out from a frozen field near Bath, Dec. 12, in Somerset, England.

The early morning frost clings to a cobweb in Regents Park on Dec.12, in London, England.

People take photos as the frost lingers on the trees at Westonbirt Aboretum on Dec. 12, near Tetbury, England.

A woman's breath can bee seen on a freezing morning in Regents Park, Dec.12, in London, England. F

Early morning frost in Hyde Park on Dec. 12, in London, England.

Thick fog covers the sky as a man walks through Buena Park Mall early Thursday, March 21 in Buena Park, Calif.

The sun rises through thick fog early Thursday, March 22 in Santa Ana, Calif.

The new China Central Television (CCTV) tower hardly visible as fog covers most of Beijing on Saturday. More than 400 flights to and from Beijing airport, including around 35 international services, were cancelled or delayed due to thick fog and strong air pollution covering the city, which the US embassy own measuring system, said pollution in Beijing had reached the "hazardous" level early March 17, before dropping one notch to "very unhealthy" later.

Vehicles make their way along a highway as fog covers most of Beijing on Saturday.

Passengers wait for their flights as almost 250 flights were cancelled, including some 15 international services, while more than 180 flights were delayed, including about 20 international services at the Beijing Capital International airport as visibility was at less than 200 metres (650 feet), official state news agency Xinhua said, blaming "widespread fog" for the disruption, in Beijing on Saturday.

Fog engulfs London Bridge as commuters make their way towards the financial district across the River Thames during the early morning rush hour in London, England on March 15, 2012.

The pods on the London Eye cast shadows against a thick morning fog as the spring sun shine begins to burn it off in central London, March 15, 2012.

Commuters walk through fog as seen from the north side of Westminster Bridge in London on March 15, 2012.

Mist and fog rolls across agricultural fields as the sun rises over the Somerset Levels on Jan. 13 in Glastonbury, England. After unseasonably mild weather, many parts of the UK were waking up to the first frost of the year. Weather forecasters have warned that there will be more hard frosts and freezing fog this weekend and temperatures will plunge across the country. Although the cold spell is only expected to last until Tuesday, the Met Office is also warning of a 'risk of colder conditions' at the beginning of February.

Mist and fog surrounds Glastonbury Tor as the sun rises over the Somerset Levels on January 13 in Glastonbury, England.

Mist and fog rolls across agricultural fields as the sun rises over the Somerset Levels on Jan. 13 in Glastonbury, England.