Delhi’s air quality index (AQI), which remained ‘moderate’ for eight days, plunged into the ‘poor’ category on Monday, prompting the Commission for Air Quality Management in NCR and Adjoining Areas (CAQM) to invoke Stage I of the Graded Response Action Plan (GRAP). The restrictions were dropped about a week ago when the AQI had improved.

Against Sunday’s average AQI of 194, the Capital on Monday clocked an AQI of 206. This month, the city so far has recorded four ‘poor’ (201-300) air days, 19 ‘moderate’ (101-200) air days, and two ‘satisfactory’ (51-100) air days.

“AQI of Delhi has shown the trend due to variable surface wind and unfavourable meteorological conditions in Delhi-NCR,” noted the Commission in its order on Monday.

Apart from calm winds, “mainly clear skies” have also influenced the meteorological conditions in the city. At 36 degrees Celsius, the maximum temperature on Monday was around five degrees above normal, as per the India Meteorological Department (IMD).