Delhi's air quality deteriorated significantly, with the overall Air Quality Index (AQI) reaching 391 on Sunday, placing it in the 'very poor' category and bordering on 'severe'. Numerous monitoring stations recorded AQI levels above 400, indicating 'severe' pollution in specific areas. A thick layer of smog and dense winter fog enveloped the city, reducing visibility and raising health concerns. Unfavorable weather conditions, including cold temperatures and calm winds, are trapping pollutants, leading to a persistent haze. Authorities are monitoring the situation and enforcing pollution control measures.