India, Nov. 20 -- A thick haze engulfed Delhi and lowered visibility as the air quality deteriorated close to the "severe" category on Thursday, with calm winds and low temperatures leading to stagnation and accumulation of pollutants.

A 24-hour average air quality Index (AQI) of 399 was recorded at 8am, compared to 392 at 4pm on Wednesday and 374 on Tuesday. The minimum temperature of 11.4degC was a degree below normal. It was 10.2degC a day earlier.

Out of the city's 39 ambient air quality monitoring stations, 20 recorded "severe" air quality. Wazirpur had the worst air quality (476), followed by Jahangirpuri (451). The Central Pollution Control Board (CPCB)'s AQI maxes out at 500.

The Air Quality Early Warning System (EWS) for Delhi...