It was 251 on Saturday, 296 on Friday, 283 on Thursday and 211 on Wednesday.
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".
The stations which recorded 'very poor' AQI include Anand Vihar, Ashok Vihar, Bawana, Dwarka sector 8, Jahangirpuri, Mundka, Narela and Rohini.
The central government's Air Quality Early Warning System for Delhi on Sunday had said that Delhi-NCR's air quality is likely to deteriorate on Monday due to unfavourable meteorological conditions.
The central agency said the AQI is likely to deteriorate to the upper end of the "very poor" category between Tuesday and Friday.
A total of 649 farm fire counts were observed over Punjab, Haryana and adjoining regions on Saturday, according to the Ministry of Earth Sciences'' air quality monitor, SAFAR. Stubble burning accounted for 12 per cent of Delhi's PM2.5 pollution on Sunday.