New Delhi: The national capital's air quality remained in the 'severe' category on Tuesday morning with an AQI of 427, while the minimum temperature dropped to 5.9 degrees Celsius, two degrees below normal.

Out of 35 monitoring stations, 28 reported 'severe' air quality, with some crossing the 450 mark, categorized as 'severe plus'. The remaining seven stations recorded air quality in the 'very poor' range, according to the Sameer app, which provides real-time data from the Central Pollution Control Board (CPCB).

An AQI above 400 is considered "severe" and poses health risks to both healthy individuals and those with medical conditions.

The weather department noted that calm winds over the past 24 hours reduced visibility, which dropped from 800 meters in shallow fog at Palam on Monday to 350 meters in moderate fog at Safdarjung on Tuesday morning. Moderate fog conditions (visibility between 200m and 500m) are expected to continue for the next two days due to prevailing calm or easterly winds.

Humidity was recorded at 97% at 8:30 AM. The maximum and minimum temperatures are forecasted to be around 24°C and 5°C, respectively.

The Centre's air quality panel for Delhi-NCR on Monday imposed the strictest Stage 4 restrictions under the Graded Response Action Plan (GRAP) due to worsening air quality. These restrictions include a ban on all construction activities, barring polluting trucks carrying non-essential goods from entering Delhi, and shifting school classes (except for grades X and XII) to hybrid mode.

The decision to implement Stage 4 curbs came shortly after the Commission for Air Quality Management (CAQM) activated Stage 3 measures earlier in the day when Delhi's AQI crossed 350.

During winters, Delhi follows the GRAP system, which classifies air quality into four stages: Stage I: Poor (AQI 201-300), Stage II: Very Poor (AQI 301-400), Stage III: Severe (AQI 401-450), and Stage IV: Severe Plus (AQI above 450).

Disclaimer: This image is taken from NDTV