In the early morning there is still thick fog over northern India and rail traffic is affected

New Delhi: A thick layer of fog enveloped the Indo-Gangetic plains in northern India on Tuesday, with poor visibility affecting road and rail traffic.

Satellite images showed a dense, elongated band of fog stretching northeast from Punjab.

A railway spokesman said 30 trains arriving in Delhi were delayed up to six hours due to the foggy weather.

At 5:30 a.m. visibility was zero meters in Varanasi, Agra, Gwalior, Jammu, Pathankot and Chandigarh; 20 meters in Gaya; 50 meters in Prayagraj and Tezpur; 100 meters in Agartala; 200 meters in Amritsar; and 300 meters in Gorakhpur.

At the Palam Observatory near Delhi's Indira Gandhi International Airport, visibility was limited to just 50 meters.

Early morning foggy weather in northern and northeastern India has severely affected road, rail and air traffic over the past two weeks.

Five flights were diverted and more than 100 flights were delayed at Delhi airport on Monday.

Civil Aviation Minister Jyotiraditya Scindia said on Monday that all stakeholders are working round the clock to minimize fog-related disruptions.

Delhi Airport has been asked to expedite commissioning of CAT III capable fourth runway in addition to the existing CAT III capable runways.

In general, CAT III compliance refers to flight operations in low visibility conditions.

As blinding fog reduced visibility to zero meters at several places, the India Meteorological Department (IMD) advised people to avoid unnecessary travel and take precautions while driving.

The IMD said dense to very dense fog is likely to continue over northern India for the next three days.

It said the northern plains would experience cold to severe days for two more days.

“Cold waves to severe cold waves are likely to persist over northwest India for three days,” it said.

In the plains, the weather department declares a cold wave when the minimum temperature drops to four degrees Celsius or when the minimum temperature is 10 degrees or less, 4.5 notches below normal.

A severe cold wave occurs when the minimum temperature drops to two degrees Celsius or the deviation from normal is more than 6.4 degrees.

A cold day occurs when the minimum temperature is no more than 10 degrees Celsius below normal and the maximum temperature is at least 4.5 degrees below normal.

A severely cold day occurs when the maximum temperature is 6.5 degrees Celsius or more below normal.