Several parts of the national capital witnessed dense fog on Saturday morning with the minimum temperature in the city settling at 6.9 degrees Celsius, two notches below the normal, the India Meteorological Department said.

The visibility at the Safdarjung observatory, which provides representative data for the city, was 100 metres at 8.30 am. The visibility at the Palam observatory was 50 metres.

The relative humidity was 100 per cent at 8.30 am.

"Observations of 0830 hrs IST, show Dense fog is persisting over Delhi (Palam 50m & Safdarjung 100m). Dense to very dense fog over Punjab (Bhiwani 25m; Amritsar, Bhatinda, Hisar 50) Dense fog over Uttar Pradesh (Agra 50m, Lucknow 100m)," the IMD tweeted.

When visibility due to fog is reduced to the range of 0 to 50 metres, it is categorised as "very dense" fog. In the case of "dense" fog, visibility is between 51 and 200 metres, "moderate" is 201 and 500 metres, and "shallow" is 501 and 1,000 metres.

The weather office has predicted dense fog during the day. The maximum temperature is expected to settle around 18 degrees Celsius, the IMD said.

Delhi's air quality was recorded in the 'moderate' category. The air quality index (AQI) at 9 am read 178, according to the Central Pollution Control Board data.

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'.

On Thursday, Delhi saw its maximum temperature go down by eight notches to 14.4 degrees Celsius, the coldest for the month of February in 19 years.

On February 1, 2003, the national capital had recorded a high of 14.3 degrees Celsius.