Delhi’s air quality deteriorated sharply on Monday, with the city’s 24-hour average Air Quality Index (AQI) plunging by more than 100 points to enter the “poor” category for the first time in nearly a month.Experts attributed this to a “mild dust storm on Sunday night”. (RAJ K RAJ /HT PHOTO)Despite the rise in pollution levels, the Commission for Air Quality Management (CAQM) decided against invoking Stage I of the Graded Response Action Plan (Grap), saying forecasts indicated that air quality would improve and remain in the “moderate” category over the coming days.At 4pm on Monday, Delhi’s AQI stood at 228, compared to 127 on Sunday – a deterioration of 101 points in 24 hours. It was the first time since May 28, when the AQI was 207, that the city recorded “poor” air quality. The last time pollution levels were worse was on May 26, when the AQI reached 252.Experts attributed this to a “mild dust storm on Sunday night”.“Because of it, the dust concentration in the air would have increased on Monday. Additionally, dry winds currently flowing over the city may have also contributed to the sudden deterioration of the air quality,” said amateur meteorologist Navdeep Dahiya.The CAQM said its GRAP sub-committee reviewed the situation and attributed the spike in pollution largely to dust storms that affected the region over the past few days.“Further, the weather/AQI forecast indicates the possibility of improvement in air quality in the coming days,” CAQM said in a statement. Based on forecasts by the India Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology (IITM), the panel concluded that Stage I restrictions were not required at present.IMD has forecast light rain and thunderstorms in Delhi on Tuesday, conditions that could help disperse pollutants and improve air quality. However, temperatures are expected to remain high.Delhi recorded a maximum temperature of 38.4 degrees Celsius on Monday. The maximum is likely to rise slightly and remain between 39°C and 41°C on Tuesday, while the minimum temperature is expected to fall from Monday’s 27.3°C to between 24°C and 26°C.Partly cloudy skies and daytime temperatures between 38°C and 41°C are expected to persist through the week.