Overnight rain cleans Delhi's air, AQI eases to 167 on Sunday morning

Delhi woke to cooler, cleaner air on Sunday after a night of thunderstorms and gusty winds. The city’s air quality index (AQI) stood at 167 at 9 am, in the moderate category, according to the Central Pollution Control Board’s data.

It was a further step down from Saturday, when the 24-hour average of 191 was already the capital’s best reading for 24 October in a decade.

The rain did not reach every corner equally. Of the 54 monitoring stations reporting, 11 were still in the poor range, above 200. IIT Delhi was the worst at 245, followed by Alipur in the north of the city at 233. PM2.5 and PM10 remained the main pollutants.

Rain and a cool morning

Safdarjung, the city’s base weather station, recorded 4.4 mm of rain between 8:30 pm on Saturday and 8:30 am on Sunday. The minimum temperature fell to 17 degrees Celsius, 0.2 degrees below the seasonal average and down from 18.3 degrees a day earlier. Relative humidity was 94 per cent at 8:30 am.

The India Meteorological Department expects mainly clear skies turning partly cloudy in the afternoon, with a maximum of around 31 degrees. Very light rain with thunder and lightning is possible at isolated places in the evening or at night. For the next two days, highs should stay between 30 and 33 degrees and lows between 15 and 17 degrees, with more scattered showers likely around the middle of the week.

Curbs stay in place

The Commission for Air Quality Management invoked Stage 1 of the Graded Response Action Plan (GRAP) across Delhi-NCR on 21 October after the air slipped into the poor range. Those measures, which include dust control at construction sites and curbs on open burning, remain in force.

On the CPCB scale, 0 to 50 is good, 51 to 100 satisfactory, 101 to 200 moderate, 201 to 300 poor, 301 to 400 very poor and above 400 severe.