Chandigarh recorded the worst air quality in the country on Thursday, with its Air Quality Index (AQI) falling in the 'severe' category for the first time this season.

The air quality in many parts of Haryana and Punjab was also recorded in the 'very poor' category and the 'poor' bracket.

Chandigarh recorded its air quality index at 427 at 12 noon, according to the Central Pollution Control Board's Sameer app, which provides hourly updates. The AQI was 460 at the ambient air quality monitoring station at Sector 22, 365 at Sector 25 and 455 at Sector 53 in the city, the data showed.

Chandigarh's air quality was worse than Delhi, which recorded its AQI at 424 at 12 noon, as per the data.

For the past few days, the air quality of the union territory continued to remain in the 'very poor' bracket, becoming one of the few cities with the worst air quality in the country.  In Haryana, the AQI was 323 in Gurugram, 299 in Panchkula, 293 in Bahadurgarh, 289 in Hisar, 269 in Sonipat, 246 in Kaithal, 223 in Kurukshetra and 228 in Yamunanagar.

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', 401 and 450 'severe' and above 450 'severe plus'.

Stubble burning in Punjab and Haryana after harvesting the paddy crop in October and November is blamed for the rise in air pollution in Delhi. As the sowing window  for Rabi crop is very short, farmers set their fields on fire to clear the crop residue.