Air pollution levels in Delhi worsened on Friday morning due to unfavourable meteorological conditions - low temperature and slow wind speed - and the air quality index read 403 at 9 am, which falls in the severe category. Low temperatures and slow surface winds allow accumulation of pollutants.
The city's 24-hour average air quality index (AQI) read 400 on Thursday evening. The air quality in the capital has remained very poor or severe on most of the days in November so far. Delhi recorded lowest air pollution levels -- in terms of 24-hour average quality index -- on November 1 (AQI 281) followed by November 23 (AQI 290).
Neighbouring Faridabad (417), Ghaziabad (373), Greater Noida (378), Gurgaon (361) and Noida (383) also saw a dip in air quality on Friday morning. 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.