New Delhi, Aug. 18 -- The Capital witnessed light showers on Sunday, which helped maintain Delhi's air quality in the "satisfactory" category, with a 24-hour average air quality index (AQI) of 91-down from a reading of 118 ("moderate")-recorded a day earlier, according to the Central Pollution Board's (CPCB's) daily bulletin. This maintained Delhi's trend of rainfall and windy conditions largely keeping Delhi's air in the "satisfactory" range, marking the 53rd time this year, the highest number of such days recorded until August 17 since 2020, according to CPCB data. In the corresponding period last year, Delhi logged 37 such days, with no "good" air day - when the AQI is 50 or lower. It logged 46 "satisfactory" air days in 2023, 44 in 2022, 36 in 2021, 76 in 2020, 28 in 2019, 28 in 2018, 27 in 2017 and only 14 such days till this point in 2016. "The cleaner air this year, compared to previous years, is largely due to the early onset of rains from May, which helped wash down pollutants. While meteorological factors have been the primary driver for more days of better air quality, minor contributions may also come from improved fuel standards, a growing fleet of BS-VI and electric vehicles, and possibly reduced construction activity," said Sunil Dahiya, founder and lead analyst at think-tank Envirocatalysts. Dahiya said the real test will come in winter, but this was still a silver lining. To be sure, the air quality was relatively better in 2020, as the Covid-19-induced lockdown curbed polluting activities. CPCB's AQI was launched in April 2015, making 2016 the first year of full data. "By implementing targeted measures to cut emissions at source, we can ensure better air quality this winter compared to past years," Dahiya said. Delhi narrowly missed out on a "good" air day last month, with the lowest AQI for the day clocked at 51 ("satisfactory") on July 15. The last time Delhi had a good air day in the period January 1-August 17 was in 2020, a lockdown year. Before that, it happened in 2019, again aided by rain. While "satisfactory" days are a sign of improvement, Delhi has also yet to record a single "severe" air day-when the AQI is over 400-this year. The last time this happened was in 2017. Delhi had three "severe" air days in the corresponding period last year, three in 2023; one in 2022; six in 2021; two in 2020, seven in 2019, six in 2018, none in 2017 and six in 2016. "We have had ample rains and consistent spells this year. May saw excess rain and since then, each month has recorded surplus rain again. It has been a combination of active weather systems and a good monsoon," said Mahesh Palawat, vice president at Skymet, stating regular spells have meant pollutants and dust keep getting washed away. On Sunday, Delhi's base weather station at Safdarjung logged 0.2mm of rainfall between 8.30am and 5.30pm. August has so far recorded 257.7mm of rainfall, an excess over the monthly normal mark of 233.1mm....