Two days before Diwali, Delhi's air quality dropped to season's worst on Friday, with the decreased wind speed leading to accumulation of pollutants and affecting dispersion.
The city's overall air quality index (AQI) fluctuated between 315 and 284 on Friday, while it was 311 on Thursday evening.
Most of the places in Delhi recorded the AQI in the "very poor" category, while the situation inched towards "severe" in some areas.
The AQI in Nehru Nagar, Ashok Vihar, Jahangirpuri, Rohini, Wazirpur, Bawana, Mundka and Anand Vihar was 340, 335, 339, 349, 344, 363, 381 and 350 respectively, according to Central Pollution Control Board.
The AQI in the neighbouring cities of Baghpat, Ghaziabad, Greater Noida, Gurgaon and Noida was 312, 336, 311, 312 and 320 respectively.
An AQI between 0 and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.
The Ministry of Earth Sciences' air quality forecast and research service, SAFAR, said, "The overall air quality is in the very poor category. Calm winds on Thursday night led to the deterioration of AQI."
A sharp deterioration of air quality, to the higher end of the very poor category, is likely on Saturday, it said.
In its Diwali forecast on Sunday, the System of Air Quality and Weather Forecasting and Research (SAFAR) said the highest impact of fire cracker emissions is expected from 1-6 am on Monday.
The impact of stubble burning is expected to be moderate and, if no additional emissions due to firecrackers occur, then the air quality would remain in middle range of very poor category on Sunday and Monday.
"However, if 50 percent of the total load of firecrackers (average of Diwali 2017 and 18) is added, the AQI may plunge to the severe category for a short period," it said.
The share of stubble burning in Delhi's PM 2.5 concentration is predicted to be 18 per cent on Saturday.
Meanwhile, the Supreme Court-mandated Environment Pollution (Prevention and Control) Authority said on Friday the construction activities in Delhi and satellite towns would be banned between 6 pm-6 am from Saturday to Wednesday.
In a letter to chief secretaries of Delhi, Haryana and Uttar Pradesh, EPCA chairman Bhure Lal also issued directions to close down coal-based industries, barring power plants, in satellite towns of Faridabad, Gurgaon, Ghaziabad, Noida, Greater Noida, Sonepat and Bahadurgarh during the period.
The ban follows a slew of recommendations from a 10-member anti-pollution task force led by CPCB Member Secretary Prashant Gargava.