On Monday, Delhi was covered in a blanket of severe haze as the city′s air quality approached the "severe" level and stubble burning accounted for 22% of the PM 2.5 pollution in the area.

The city′s 24-hour average air quality index (AQI), which was 352 on Sunday, was now 392 (extremely poor). On Thursday, AQI was 354, followed by 271 on Wednesday, 302 Tuesday, and Monday (Diwali day) reported 312.

According to the Indian Agricultural Research Institute (IARI), Punjab saw 2,131 farm fires on Monday, the most so far this season. On Monday, IARI reported 70 and 20 cases of stubble burning in Haryana and Uttar Pradesh, respectively.

SAFAR, a forecasting organization under the Ministry of Earth Sciences, estimates that 22% of Delhi′s PM2.5 pollution on Monday was caused by farm fires. So far, the greatest percentage this year was 26% on Sunday and just 21% on Saturday.

Mr. Mahesh Palawat, vice president (meteorology and climate change), stated that the low wind speed caused contaminants to build up in the air worsening the air quality index scenario to "severe" on Tuesday morning. He added that the direction and speed of the wind at the transport level favoured the movement of smoke from stubble burning.

The Delhi Pollution Control Committee found that between November 1 and November 15, when stubble burning reaches its height, and average PM2.5 concentrations are at 285 micrograms per cubic metre, citizens in the capital of India breathe the dirtiest air.

(Source: https://health.economictimes.indiatimes.com/news/industry/as-dense-layer-of-smog-envelops-delhi-air-quality-nears-severe-zone/95217423)