New Delhi:  Delhi woke up to dense fog on Friday morning and the resultant low visibility hampered road, rail and air traffic affecting commuters adversely.

Chilly winds blew across the city with the minimum temperature recorded at 6.6 degrees Celsius. At 8.30 a.m., visibility was reduced to less than 100 metres, and road traffic was forced to slow down to a crawl.

A railway official said 25 trains were cancelled and over 15 were delayed due to fog.

'Over 15 trains were running behind schedule by several hours and 25 trains have been cancelled. Dense fog across many parts of north India affected rail services,' a Northern Railway spokesperson said.

The fog also disrupted operations at the Indira Gandhi International (IGI) airport, with many flights getting delayed and some cancelled due to the heavy fog.

'Over 40 domestic and international flights have been delayed, while nine arriving and departing flights were cancelled,' an airport official said.

Visibility at the runway dropped to 50 metres and as a result no flights could take off for some time early morning. The minimum visibility is 125 metres and 150 metres for various categories of aircraft.

'The visibility hovered around 50-75 metres. Some flights landed using CAT III B instrument landing system, which allows a aircraft to land when the runway visibility is 50 metres,' the official said.

An India Meteorological Department (IMD) official said: 'The visibility will improve as the day progresses.'

Early morning commuters had a tough time steering through the fog on the capital's roads.

Gurgaon was hit hard as some even found it difficult to leave their houses. 'There was dense fog. I could not even leave my home as nothing was visible in the fog,' said an resident of DLF.

The minimum temperature was a notch below the average for this time of the season, the IMD official said. The maximum temperature is expected to hover around 23 degrees. Humidity at 8.30 a.m. was 97 percent.

On Thursday, the minimum and maximum temperatures were recorded at 6.8 and 22.3 degrees, respectively.

The Met department said the coldest day of the season so far has been December 25 when the minimum temperature dropped to 2.9 degrees Celsius.

(Agencies)