After oscillating between the "good" and "satisfactory" categories for one-and-half-month, the national capital's air quality dropped to the "moderate" category on Saturday.
Experts attributed it to lack of favourable wind speed and rains over the last few days.
The city recorded a 24-hour average air quality index (AQI) of 101. The last time Delhi recorded its AQI (124) in the moderate category was on July 15.
AQI between 0 and 50 is considered safe, 51-100 satisfactory, 101-200 moderate, 201-300 poor. At 301-400, it is considered very poor and 401-500 falls in the severe category. The above 500 is severe as well as the emergency category.
A Central Pollution Control Board (CPCB) official said the air quality deteriorated slightly due to lack of rains and favourable wind speed. However, rains on Saturday evening will lead to some improvement.
On August 31, it recorded a 24-hour average AQI of 41, which was the lowest since the CPCB started maintaining air quality records in 2015.
It was the fifth "good" day in terms of air quality this year.
AQI values were 45, 50, 50 and 45 on March 28, August 13, August 20 and August 24, respectively.
The AQI value remained between 50 and 70 on most days in August.
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