NEW DELHI: Delhi woke up to its worst air quality of the season on Tuesday, with the AQI plunging to into the "severe" category at 423.

The Centre invoked stricter anti-pollution measures under Stage III of the Graded Response Action Plan (GRAP) in the wake of the deteriorating air quality.

On Monday, the Central Pollution Control Board's (CPCB) 24-hour average AQI data showed that Delhi's air quality was 'very poor' with an Air Quality Index (AQI) of 362.

As per the CPCB classification, an AQI between 0 and 50 is considered "good", 51 to 100 "satisfactory", 101 to 200 "moderate", 201 to 300 "poor", 301 to 400 "very poor", and 401 to 500 "severe".

Since Diwali, the national capital's air quality has consistently remained in the 'poor' or 'very poor' category, occasionally slipping into the 'severe' zone.

Temperatures in the city, too, have continued to dip since last week. The minimum temperature was recorded at 10.2 degree celsius 4.1 notches below normal on Tuesday, while the maximum was likely to settle around 28 degree Celsius.

On Monday, the city also reported its first cold wave of the season, with the Aya Nagar station recording a minimum temperature of 9.9 degree Celsius.