Mumbai on Friday once again recorded an Air Quality Index (AQI) of 317 which was worse than that of Delhi, an official of the India Meteorological Department said.
The mercury is likely to increase slightly on Sunday and Monday under the influence of a fresh western disturbance affecting the upper reaches of the Himalayas.
For the plains, the IMD declares a cold wave when the minimum temperature is 10 degrees Celsius or below and is 4.5 notches less than normal for two consecutive days. However, for small areas such as Delhi, a cold wave can be declared if the criteria is fulfilled even for a day.
According to the IMD, a "cold day" is when the minimum temperature is less than 10 degrees Celsius and the maximum is at least 4.4 degrees Celsius below the normal. A "severe" cold day is when the maximum temperature is at least 6.5 notches below the normal.
The air quality over Delhi and National Capital Regional Area is likely to improve marginally but remain in the upper end of the "Very Poor" category according to IMD.
Stubble burning has stopped now but Delhi's air pollution situation remains serious, Union Environment Minister Prakash Javadekar said on Friday urging the Arvind Kejriwal government to take swift action on the complaints forwarded to it by the CPCB.
The minimum temperature this season has remained 2-3 degrees Celsius below normal in the absence of a cloud cover on most days, according to IMD officials.
The 24-hour average was 231 on Saturday, 137 on Friday, 302 on Thursday and 413 on Wednesday.
Central Pollution Control Board (CPCB) Member Secretary Prashant Gargava on Thursday assured that the air quality will substantially improve in coming years and that the country is on a right track in curbing the menace.
After the national capital saw more than a 100 Covid-19 deaths for four consecutive days, Delhi Health Minister Satyendar Jain on Monda attributed the high COVID-19 death rate in the city to the pollution caused by stubble-burning and expected a downtrend in it in the next two-three weeks.
The newly-appointed Commission for Air Quality Management on Monday said it will take required steps to curb air pollution in the national capital, including formulation of appropriate policies and strategies to control stubble burning.
Delhi's air quality remained "poor" on Sunday and government agencies said it is likely to deteriorate further due to unfavourable meteorological conditions.
The air quality remained 'very poor' in Noida, Greater Noida, and Ghaziabad on Friday while it was in the 'poor' zone in Faridabad and Gurgaon in the National Capital Region (NCR), according to a government agency.
Delhi's air quality was recorded in the "poor" category on Thursday as the share of stubble burning in the city's pollution increased to 20 percent.
Delhi's air quality deteriorated marginally and was recorded in the "poor" category on Wednesday as a change in the wind direction increased the share of stubble burning in the city's pollution slightly.
Delhi's air pollution went down drastically on Wednesday as gusty winds and rains helped flush out key pollutants leading the AQI to improve from 'poor' to 'moderate' category.
The national capital recorded its air quality in the 'very poor' category on Friday and it was likely to become 'severe' on Diwali night, according to government agencies.
Air quality in Delhi continues to be in the 'very poor' category, even after a slight improvement in the level of pollution was recorded. On Thursday, experts asserted the pollution situation was much better as compared to previous days, when the pollution had almost touched 'emergency' levels.
The Ministry of Earth Sciences' air quality monitor, SAFAR, said that under 'zero-firecracker' scenario, the level of PM2.5 is likely to be the lowest in the past four years as not so calm surface winds in Delhi will help in dispersion (of pollutants).