Against expectations, air quality in the national capital improved significantly on Thursday thanks to light rain and strong winds. The forecast for the rest of the week, however, is grim.

On Thursday, the Air Quality Index (AQI) improved from “very poor” to “moderate. It had dropped from Wednesday’s 392 at 4pm to 194, giving Delhi it’s cleanest day in December so far.

Light rain over the past 24 hours along with strong winds were the major factors responsible for cleansing the air, said scientists of Safar, the government’s air quality forecasting agency.

“Rainfall over the night and moderate wind speed were sufficient enough to wash away the pollutants significantly. However, respite may not last long, as relative humidity is very high while the temperature is also expected to cool down further, both of which are not favourable for dispersion of pollutants. In case surface wind speed slows down, which is likely by Friday evening, pollution can again start building up pushing the air quality in ‘very poor’ category over the weekend,” said a statement issued by Safar.

Earlier forecasts had predicted the AQI to remain in the “upper end of very poor category”. Delhi had last witnessed ‘moderate’ air quality on November 4, which was the cleanest November day in at least three years.

According to officials in the India Meteorological Department (IMD), the wind speed on Thursday fluctuated between 10 kmph and 12 kmph, favourable for dispersion of pollutants.

“Wind speed is likely to remain on an average of 8 kmph till December 15. It may slow down on December 16 along with a drop in minimum temperature, triggering some deterioration in air quality,” said, a scientist of the IMD’s regional weather forecasting centre (RWFC).

Also, as per the forecast, minimum temperature is going to drop to around 7 degrees Celsius on Saturday, which would be at least two notches below normal.

On Thursday the minimum temperature was recorded as 11.2° Celsius, three degrees above the season’s average. The maximum temperature stood at 20.8°Celsius, which was two notches below normal. “The minimum temperature has been high over the past few days because of western disturbance. However, it is likely to fall over the weekend, because of strong and cold winds from the northwest are likely to reach Delhi. Snowfall in northwestern region will trigger cold winds,” said, Kuldeep Srivastava, head, RWFC.

First Published: Dec 14, 2018 09:58 IST