October begins with a familiar air quality slide

Air quality in the Capital continued to deteriorate on Thursday, with the first day of October marking the lowest air quality over the past week

Air quality in the Capital continued to deteriorate on Thursday, with the first day of October marking the lowest air quality over the past week. According to the Central Pollution Control Board (CPCB) data, Delhi’s air quality index (AQI) was 166, categorised as “moderate” on the day, which was worse than the AQI of 129 recorded the day before and at least five days of “satisfactory” air preceding that.

The CPCB identified PM10 (particulate matter having a diameter of 10 microns or less) as the prominent pollutant in the city. (Sanchit Khanna/Hindustan Times)

The CPCB identified PM10 (particulate matter having a diameter of 10 microns or less) as the prominent pollutant in the city. The deterioration came as the effect of recent rainfall on pollutant dispersion weakened.

“The relatively clean air over the past few weeks has been sustained by lingering monsoon ventilation dynamics and a notable delay in stubble-burning activity across Punjab and Haryana. However, this is a calm before the seasonal storm. As harvest activity accelerates alongside festival celebrations, atmospheric dispersion will sharply decline. Unless year-round baseline emissions from power plants, heavy industries, waste sector, and vehicular transport are permanently abated, Delhi’s seasonal air quality slump remains an inevitable reality,” said Jinitha Varghese, program manager, EnviroCatalysts.

An AQI between zero and 50 is considered “good”, 51 to 100 “satisfactory”, 101 to 200 “moderate”, 201 to 300 “poor”, 301 to 400 “very poor”, and 401 to 500 “severe”.

Neighbouring NCR cities also clocked similar AQIs on the day, with Noida clocking the worst AQI of 194. Ghaziabad recorded an AQI of 191, Greater Noida clocked 116 and Gurugram clocked 182, as per the CPCB’s daily bulletin.

Meanwhile, the temperature started to rise in the Capital, with the minimum clocked at 24°C, which was up from the reading of 22.4°C recorded the day before and 0.7°C above normal. The maximum temperature was 35.2°C, up from the maximum of 34.2°C recorded the day before and 0.5 degrees above normal, according to the India Meteorological Department (IMD).

The city remained largely dry through the day, with the IMD recording no rainfall. The Ridge, however, continued to be considerably cooler than other parts of the city, recording a minimum of 19.6°C, which was 3.3 degrees below normal.

“The weather system that brought rain and cooler conditions last week to Delhi has weakened. As cloud cover and rainfall activity reduce, temperatures are rising,” an IMD official said.

The extended range forecast released by the IMD on Thursday indicates that the dry spell is likely to continue for the next few days, but a change in weather conditions is expected around October 7.

According to the forecast, an active western disturbance is likely to affect northwest India during the first week of October. Under its influence, isolated to scattered rainfall is likely over Haryana, Chandigarh, Delhi and Punjab on October 6 and 7. The same period is expected to bring rainfall to parts of Jammu and Kashmir, Ladakh, Himachal Pradesh and Uttarakhand, with rainfall also likely over Uttar Pradesh on October 7.

The IMD’s observations showed that while temperatures have begun rising again, the extended forecast does not indicate a return of heatwave conditions. The October 6-7 weather system is expected to bring another spell of cloud cover and scattered rain to the Capital, potentially marking the next significant change in Delhi’s weather after the current dry spell.