For Delhi residents, the rain over the past few days has brought relief not only from the sweltering heat, but now also from the air pollution that incessantly plagues the city.

Delhi on Thursday recorded the cleanest air the city has seen in nearly 300 days, as the 24-hour average air quality index (AQI) reading fell to 61 in the satisfactory category. This is the best air Delhi has seen since September 11, 2023, when it was 53, according to Central Pollution Control Board (CPCB) data.

On-and-off spells of rain in the city in the past 24 hours, coupled with strong winds, were the reason for the improvement in air quality, weather scientists said.

The rain also continued to offer relief from the heat. Overcast skies throughout the day meant that the maximum temperature in the city was lodged at 31.7 degrees Celsius (°C), six degrees below what is considered normal for this time of the year. A day earlier on Wednesday, it was 34.1°C

Delhi’s minimum similarly fell to 24.8°C on Thursday, three notches below normal. It was 29°C on Wednesday.

A day’s AQI reading is taken at 4pm daily, which is the average AQI of the 24 hours preceding it. On Wednesday, the 4 pm reading was 108 (moderate). Prior to Thursday, the lowest AQI this year was 64 (satisfactory) on June 28, after Delhi saw a record-breaking spell of 228.1mm rain.

An AQI reading between 51 to 100 is classified as “satisfactory”, between 101 and 200 is classified as “moderate”, between 201 and 300 is classified as “poor”, between 301 and 400 is classified as “very poor” and over 400 is “severe” by the CPCB.