Delhiites breathed a sigh of relief on Wednesday as the air quality in the national capital improved significantly due to rains and favourable wind speed.
The city's air quality index (AQI) read 133, in the "moderate" category, at 7 pm.
While most of the 37 air quality monitoring stations in Delhi recorded AQI in the "moderate" category, air quality at a few places like Lodhi Road, Pusa, Aurobindo Marg and Burari Crossing improved to "satisfactory" levels.
An AQI between 0-50 is considered 'good', 51-100 'satisfactory', 101-200 'moderate', 201-300 'poor', 301-400 'very poor' and 401-500 'severe'. An AQI above 500 falls in the 'severe plus' category.
The level of PM2.5 -- tiny particulate matter less than 2.5 microns in diameter that can enter the lungs and the bloodstream -- in Delhi and National Capital Region (NCR) was 56.5 microgram per cubic metre at 7 pm. The region had last recorded such levels (59.7) on October 19.
The national capital and its suburbs recorded light rains on Wednesday. A few areas in the region also received hail. Most areas in Haryana and Punjab recorded "satisfactory" or "good" air quality, the first time in the last two months.
Experts said this happened as paddy straw burning has almost stopped and rains in the two agrarian states reduced the leftover impact of farm fires.
"Haryana received widespread rains on Tuesday and Wednesday. Punjab also got moderate rains," a senior official of India Meteorological Department (IMD) said.
The wind direction changed from southeasterly to northwesterly in the afternoon but that didn't affect the air quality in Delhi-NCR as farm fires have reduced considerably, he said.
Favourable wind speed (more than 15 kilometers per hour) cleared the pollutants faster. The Centre-run System of Air Quality and Weather Forecasting and Research (SAFAR) said, "Precipitation recorded in Delhi and northwestern regions under the influence of western disturbance has washed out suspended pollutants and led to rapid improvement in air quality."
Forecast suggests the AQI is likely to remain in the "moderate" category on Thursday and would dip to the "poor" category on Friday, it said.