A sustained spell of rain on Sunday brought a significant improvement in air quality in the capital, yielding the second "good" air day of the year, according to Central Pollution Control Board (CPCB) data. The 24-hour average air quality index in the city was 48 at 4 pm. It was 56 on Saturday and 55 on Friday.
The neighbouring cities of Ghaziabad (14), Gurugram (32) and Greater Noida (23) also recorded 'good' air quality. Noida recorded a 24-hour average AQI of 55 at 4pm, which falls in the "satisfactory" category.
Before this, Delhi had recorded a 24-hour average AQI of 47 on September 16.
An 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', and 401 and 500 'severe'.
The national capital has recorded 128 days of bad air quality (AQI is poor, very poor or severe) this year so far, the highest since 2017, when it saw 130 such days during the corresponding period. Delhi received 74 mm of rainfall in 24 hours ending 8.30 am, the second highest rainfall since 2007, according to the India Meteorological data.The Palam observatory recorded 64.9 mm rainfall. The Lodhi Road, Ridge, and Ayanagar weather stations received 87.2 mm, 60.1 mm, and 85.2 mm rainfall respectively. The difference between minimum temperature (20.8 degrees Celsius) on Friday and maximum temperature (23.4 degrees Celsius) on Saturday was 2.6 degrees Celsius — the lowest since 1969, an IMD official said.