As per the System of Air Quality and Weather Forecasting and Research (SAFAR), Delhi’s air quality turned 'very poor' with overall air quality index (AQI) standing at 301. The temperature has dipped further in Delhi-NCR. Low-level visibility was witnessed in several parts of the national capital on January 13. A thick layer of fog blankets the city today. Cold waves have tightened its grip in Delhi and adjoining cities. Delhi recorded a minimum temperature of 4.8 degree Celsius today.