Delhi's air quality was recorded in the 'severe' category Sunday due to a reduced wind speed even as authorities have forecast rainfall in the next couple of days which they said might lower the pollution level. According to Central Pollution Control Board (CPCB) data, the overall air quality index (AQI) in the city was 416, which falls in the 'severe' category. An AQI between 100 and 200 comes under the 'moderate' category, 201 and 300 is considered 'poor', 301 and 400 'very poor', while that between 401 and 500 is 'severe'. As many as 24 areas recorded 'severe' air quality and seven 'very poor' air quality, the CPCB said. In the National Capital Region (NCR), Ghaziabad, Faridabad, Noida and Greater Noida recorded 'severe' air quality, it said. The overall PM2.5 level - fine particulate matters in the air with a diameter of less than 2.5 micrometers - in Delhi was at 273, while the PM10 level was at 426, it said. The Centre-run System of Air Quality and Weather Forecasting (SAFAR) said the air quality may improve in the next two days under the influence of light rains which is expected thereafter. Read Also| Bill prohibiting commercial surrogacy evokes mixed response\u00a0 "The overall air quality will deteriorate further, with small fluctuations in the next three days if it does not rain. Other meteorological conditions are not favourable although foggy conditions are likely to reduce now," the SAFAR said. It said the air quality will deteriorate further by Sunday to remain in the border of very poor to severe and then to start improving depending on rain. "In any case, the AQI will start receding by Tuesday but to remain in very poor. Other meteorological conditions are not favourable although foggy conditions are likely to reduce now," it said. Delhi's air quality was recorded in the 'poor' category Wednesday and Thursday with increased wind speed which helps in cleansing the air before slipping into very poor category Friday afternoon, the air quality slipped to severe category.