The air quality was recorded in the 'very poor' category.
Delhi recorded the season's coldest morning on Monday with the minimum temperature settling three notches below normal at 6.5 degrees Celsius, the Met office said.
The minimum temperature recorded at the observatory at Lodhi Road was 6.3 degrees Celsius, two notches below normal, it said. The air quality was recorded in the 'very poor' category.
The maximum temperature was recorded at 24.8 degrees Celsius, normal for this time of the year.
The national capital has been witnessing below-normal temperatures during the last couple of days. On Saturday, the city recorded a low of 8.5 degrees Celsius. On Sunday, the minimum temperature was recorded at 8.3 degrees Celsius.
The forecast for the period between December 12 and 17 indicates that the minimum temperature will oscillate between 6 and 8 degrees Celsius.
At 4 pm, Delhi's 24-hour average Air Quality Index (AQI) stood at 317.
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', 401 and 450 'severe' and above 450 'severe-plus'.
On Monday, the humidity levels oscillated between 40 per cent and 100 per cent.
The weather office has forecast clear skies for Tuesday with shallow fog in the morning.
The maximum and minimum temperatures are likely to settle around 24 and 6 degrees Celsius, respectively. The air quality is likely to remain 'very poor' till Thursday.