New Delhi: The weather department has issued an "orange alert" for dense fog on Saturday in the national capital and adjoining areas, officials on Friday said.

The India Meteorological Department (IMD) has forecast mainly clear skies with dense to very dense fog during the early hours.

There will be cold to severe cold day condition at isolated places in Delhi, with maximum and minimum temperatures likely to settle around 15 and 7 degrees Celsius, respectively, they said.

Kuldeep Srivastava, scientist and head of the Regional Weather Forecasting Centre, said there will be a marginal increase in the maximum temperature next week.

"Mornings and evenings in Delhi will be cold. However, there will be relief during the daytime due to sunlight," he said.

He added there will be no significant change in Delhi's weather conditions in the month of January so far.

The national capital is continuously experiencing a foggy and cold week, with the maximum temperature on Friday settling at 14.2 degrees Celsius, five notches below the season's average.

On Friday, cold to severe cold conditions were observed across Delhi.

The minimum temperature settled at 7.1 degrees Celsius in Delhi, with a thick layer of fog enveloping several parts of the city, affecting rail, runway and road traffic.

The visibility at the Indira Gandhi International Airport was recorded at 500 meters at 8.30 am, as per the IMD.

Due to foggy conditions, at least 22 Delhi-bound trains or those having a route through the national capital were running late as on January 19, according to railway officials.

As per the data by the Central Pollution Control Board (CPCB), the overall Air Quality Index (AQI) at 4 pm stood at 348 under 'very poor' category.

An AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.