The noxious haze returned to Delhi and its suburbs on November 12 with raging stubble fires in neighbouring states, fall in the temperature and wind speed pushing the city's air quality in the "severe" zone.
The government's air quality monitor, SAFAR, said pollution levels in Delhi-NCR are expected to enter the "severe plus" or "emergency" category on Wednesday.
Meteorologists said the national capital recorded on Tuesday morning a minimum temperature of 11.7 degrees Celsius, the season's lowest so far. It is two notches below normal for this time of the year.
A dip in wind speed and temperature makes the air cold and denser, leading to accumulation of pollutants, said Kuldeep Srivastava, head of the India Meteorological Department's regional weather forecasting centre.