A thick grey haze hung over the capital on Monday while the air quality settled in the 'very poor' category, with the 24-hour average AQI recorded at 373.
Out of the 39 functional monitoring stations, 12 logged readings in the 'severe' category, while 27 recorded 'very poor' air quality.
Among the stations in the severe zone, Anand Vihar emerged as the most polluted, logging an Air Quality Index (AQI) of 425, according to the CPCB's SAMEER app.
Delhi also recorded the worst air quality in the National Capital Region, followed by Noida at 366, according to Central Pollution Control Board (CPCB).
According to CPCB standards, an AQI between 0 and 50 is considered 'good', 51 to 100 'satisfactory', 101 to 200 'moderate', 201 to 300 'poor', 301 to 400 'very poor' and 401 to 500 'severe'.
Data from the Decision Support System for Air Quality Management showed that vehicular emission was the largest contributor to pollution, accounting for 15.7 per cent of the total share.
This was followed by industries in Delhi and peripheral areas, contributing 7.1 per cent, residential sources 3.8 per cent, construction activities 2.0 per cent, and waste burning 1.3 per cent.
Among NCR districts, Gurugram contributed 8.6 per cent, Jhajjar 8.5 per cent, Bharatpur 5.1 per cent, Faridabad 4.8 per cent, Sonipat 4.6 per cent, Ghaziabad 2.7 per cent, and Rohtak 2.0 per cent, the data showed.
According to the Air Quality Early Warning System, Delhi's air quality is likely to remain in the very poor category from Tuesday to Thursday, and is expected to oscillate between very poor and severe levels over the next six days.
This December, the air quality has persistently remained in the red zone with AQI readings above 300 from December 1 to 8.
The city saw brief relief for two consecutive days when pollution levels dipped to the 'poor' category, before returning to the red zone on December 11 and remaining there since, according to CPCB data.
Apart from those two days, Delhi air has largely remained 'very poor', with AQI levels hovering above 300 for most of the month.
Earlier in the day, thick haze shrouded the city, with morning AQI readings remaining in the very poor category at 366.
The AQI at seven air quality monitoring stations was 'severe', with Narela logging the highest reading at 418.
Meanwhile, the India Meteorological Department said Delhi recorded a maximum temperature of 21.8 degrees Celsius, 1.1 notches above normal, and a minimum temperature of 11.0 degrees Celsius, 3.5 degrees above normal.
Relative humidity stood at 100 per cent at 8:30 am and 79 per cent at 5:30 pm, it said.
The IMD had forecast a minimum temperature of 10 degrees Celsius, and a maximum of 22 degrees Celsius, accompanied by moderate fog.
It also predicted a prevailing average wind speed of less than 10 km per hour, unfavourable for the dispersion of pollutants, likely prolonging the spell of poor air quality in the capital.