Delhi records cleanest Oct air in 4 years; AQI dips to 60

The rain also produced an unusually low maximum temperature of 20.7°C, a record for October in data dating to 1951.

A spell of heavy rain, rare for October, washed the pollution out of Delhi’s air on Friday and gave the Capital its cleanest October day in four years. Residents woke to a cold, wet morning, and the temperature at Safdarjung rose no higher than 20.7°C, the lowest October maximum in records going back to 1951.

Friday’s maximum was 10.3 degrees below normal. (Vipin Kumar/Hindustan Times)

With Friday’s official air quality index (AQI) reading of 60, in the “satisfactory” category, Delhi is poised to record its cleanest October since the Central Pollution Control Board (CPCB) began its daily AQI bulletins in 2015. The average for the first 30 days of the month stands at 167.

Friday’s maximum was 10.3 degrees below normal. Safdarjung, the city’s base weather station, recorded 61.4mm of rain in the 24 hours ending 8.30am on Friday, the sixth-highest 24-hour rainfall for October since 1951. The rain and thunderstorms followed the interaction of Cyclone Arnab with a western disturbance, a weather system that carries moisture in from the west.

“An unusual convergence of multiple weather systems led to this spell of unsettled weather across northern and eastern India. A western disturbance over the western Himalayas, extending its influence towards Jammu, an induced cyclonic circulation over southern Punjab, and a depression over North Chhattisgarh collectively contributed to an abundant influx of moisture,” Mahesh Palawat, vice-president of meteorology and climate change at Skymet Weather, told HT.

The weather systems are now weakening and moving away. “From Saturday onwards, we expect maximum temperatures to gradually rise towards 29–30°C, bringing a noticeable improvement in daytime weather conditions,” Palawat said.

The AQI in CPCB’s 4pm bulletin fell 162 points from 222 (“poor”) on Thursday, the fourth-largest one-day fall for an October day since 2015. Friday’s air was the cleanest since September 28 this year, when the AQI was 56 (“satisfactory”).

Under CPCB standards, an AQI of 0–50 is “good”, 51–100 “satisfactory”, 101–200 “moderate”, 201–300 “poor”, 301–400 “very poor” and 401–500 “severe”.

Before Friday, Delhi had recorded an AQI of 60 or below on only five October days since 2015, according to an HT analysis: October 18, 2021 (46), and October 7, 8, 9 and 10, 2022 (55, 56, 48 and 44). Both of those spells also came with heavy October rain: 87.9mm fell on October 18, 2021, and 74.3mm on October 9, 2022.

Friday’s reading is also the lowest for October 30 in the bulletin’s records. Between 2016 and 2025, the AQI on this date ranged from 268 to 431.

The average for October 2026 so far is already below the previous best monthly average of 173, recorded in October 2021. October averaged 210 in 2022, 219 in 2023, 223 in 2025, and 234 in both 2019 and 2024. In the other years between 2015 and 2020, the monthly average ranged between 264 and 285.

October 2026 will stay the cleanest unless Saturday’s bulletin reads 352 or higher, in the “very poor” category, a jump of almost 300 points in a day.

At 20.7°C, Friday’s maximum broke the previous October low of 21.5°C, recorded on October 25, 1975, according to India Meteorological Department (IMD) data. Next were 21.9°C on October 31, 1961, 22.1°C on October 18, 1971, and 22.2°C on October 1, 1954. The minimum was 17.2°C, 1.1 degrees above normal.

recorded another 4.2mm of rain between 8.30am and 5.30pm on Friday. Palam recorded 43.1mm in the 24 hours to 8.30am and another 3mm by 5.30pm. Lodhi Road recorded 67.4mm by 5.30pm, Ridge 52.2mm and Ayanagar 57.5mm.

The highest 24-hour rainfall for October at Safdarjung was 172.7mm, recorded on October 1, 1954, followed by 110.9mm on October 9, 1956. The third-highest was 87.9mm on October 18, 2021, followed by 74.3mm on October 9, 2022, and 68.3mm on October 3, 2004.

The month’s rainfall at Safdarjung has now reached 123.3mm, making October 2026 the fourth-wettest October at the station since 1951. It has passed the 122.5mm recorded in October 2021. The wettest was 1954, with 238.3mm, followed by 236.2mm in 1956 and 128.6mm in 2022.