Delhi on Saturday recorded its lowest minimum temperature of the season at 3.6 degrees Celsius and thick fog blanketed several parts of the city, the India Meteorological Department (IMD) said.
On Friday, the national capital had recorded a minimum temperature of 3.9 degrees Celsius, the lowest in five years.
The maximum temperature on Saturday is likely to settle around 19 degrees Celsius, the IMD said.
The visibility at Safdarjung Observatory, Delhi's main weather station, was 200 metres at 5:30 am, it said.
According to the Railways, 18 Delhi-bound trains were delayed by one to six hours due to the fog.
According to the IMD, very dense fog is when visibility is between 0 and 50 metres, between 51 and 200 metres is dense, between 201 and 500 metres moderate, and between 501 and 1,000 metres shallow.
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Delhi's Air Quality Index (AQI) stood at 365 at 9 am, according to Central Pollution Control Board (CPCB) 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'.