According to the System of Air Quality and Weather Forecasting And Research (SAFAR), the overall AQI docked at 356 at 9 am, which falls in the 'very poor' category.
At Chandni Chowk, the AQI was recorded at 321, 355 in Lodhi Road, 346 in IGI airport and 331 in IIT Delhi.
An AQI between 0-50 is considered good, 51-100 is satisfactory, 101-200 moderate, 201-300 poor, 301-400 very poor and 401-500 is marked as severe or hazardous.
The India Meteorological Department (IMD) has forecast a generally cloudy sky with the possibility of light rain with maximum and minimum temperatures at 23 and 9 degrees Celsius, respectively.
On Sunday, the maximum and minimum temperatures in the national capital were recorded at 24.3 and 7.1 degrees Celsius respectively.
"Scattered to fairly widespread rain or thunderstorm with isolated heavy falls accompanied with hail or lightning also likely over north Punjab, north Haryana and northwest Uttar Pradesh on Monday," the IMD said in its bulletin.
A fresh western disturbance in quick succession is also very likely to affect the Western Himalayan region and plains of northwest India from January 15 onwards with a peak intensity of precipitation on January 16, the weather agency added.
As many as 15 trains are running late due to low visibility in the Northern Railway region.