Delhi-NCR's air quality bordered "severe" levels on Monday with more farm fire plume blowing towards the region, and a decrease in the wind speed and temperature hampering dispersion of pollutants.
The Ministry of Earth Sciences' air quality monitor, SAFAR, said the air quality will turn "severe" on Tuesday.
On Monday, the city's overall air quality index read 360 at 4 pm, up from 321 on Sunday.
The monitoring stations at Nehru Nagar (406), Ashok Vihar (402), Rohini (414), Vivek Vihar (406), Wazirpur (409), Bawana (414), Mundka (413), and Anand Vihar (412) recorded the air quality in the "severe" category.
Pollution levels in Ghaziabad also entered "severe" levels towards the evening, and increased in Greater Noida (392) and Noida (400).
An AQI between 201 and 300 is considered 'poor', 301-400 'very poor' and 401-500 'severe'. An AQI above 500 falls in the 'severe plus' category.
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Kuldeep Srivastava, head of the India Meteorological Department's regional weather forecasting centre, said the spike in pollution levels can be attributed to a significant decline in the wind speed -- from 20 kilometers per hour over the last two days to 10 kilometers per hour on Monday.
He said incidents of stubble burning in Haryana and Punjab have increased and northwesterly winds have been bringing more farm fire plume to the Delhi-NCR region.
A dip in the temperature has also led to accumulation of pollutants near the ground, he said.
SAFAR said the effective stubble fire count on Sunday was 1,846.
"Stubble plume intrusion is expected to increase and a decrease in surface wind speed over the Delhi region is predicted for the next two days," it added.
In view of this, the share of farm fires in Delhi's air pollution is simulated to be 25 per cent on Tuesday, SAFAR said.
A western disturbance is located as a cyclonic circulation over Jammu and Kashmir and adjoining north Pakistan. Under its influence, skies over Delhi-NCR will be partly cloudy and the temperature will dip which may lead to accumulation of pollutants near the ground, SAFAR said.
Meanwhile, the Supreme Court-mandated anti-pollution authority EPCA on Monday said dirty fuel-based industries in Delhi and its suburbs will remain shut till the morning of November 13.
The Environment Pollution (Prevention and Control) Authority also extended the ban on hot-mix plants and stone-crushers in Delhi-NCR till Wednesday morning.