Delhi's air quality deteriorated into the 'Severe' category on Saturday morning, with an overall AQI of 422 after showing a slight improvement on Friday. Out of 39 monitoring stations, 28 reported 'Severe' AQI, while the rest showed 'Very Poor' levels. Wazirpur recorded the highest AQI at 467, followed by Jahangirpuri at 463, and Anand Vihar at 458, CPCB data revealed.