New Delhi, Jan 19 : The residents of the national capital on Tuesday woke up to a foggy morning with the minimum temperature settling at 7.4 degree Celsius. The people continued to breathe polluted air, as the Air Quality Index (AQI) in Delhi was 256 for PM10 and 148 for PM2.5. As the PM10 was on a high scale, the System of Air Quality and Weather Forecasting And Research (SAFAR) has issued a health advisory stating that sensitive people should consider reducing prolonged or heavy exertion and heavy outdoor work. The PM2.5 level was under the 'very poor' category. Usually, the air quality is categorised as 'good' when the AQI is between 0 to 50; 'satisfactory' between 51-100; 'moderate' between 101-200; 'poor' between 201-300; 'very poor' between 301-400; 'severe' between 401-500; and 'hazardous' at over 500. Delhi, generally, has good to satisfactory air quality. However, the pollution levels during October to February due to various factors including stubble burning, road dust, vehicle pollution, and cold weather lead to a deterioration in the AQI. As the day progresses, the weather agency has predicted a cold day with shallow fog in some areas. The maximum temperature is likely to hover around 16 degrees Celsius and the minimum may remain steady at 7 degrees. According to the morning update, a temperature of 7.4 degrees Celsius was recorded at 8.30 a.m. with a relative humidity of 97 per cent. Cold wind was blowing in the East-southeasterly direction at a speed of 3.6 km per hour. The city observed sunrise at 7.15 a.m. and the sun is likely to set at 5.50 p.m.In the past 24 hours, the maximum temperature was recorded at 15.4 degrees Celsius, a notch above normal. /IANS