A thick layer of fog stretching from Punjab to Bihar reduced visibility across the Indo-Gangetic plains on Friday morning, with the India Meteorological Department (IMD) issuing a red alert for Delhi and warning that road, rail and air traffic may be affected. (Pics/PTI)

Dense fog and a severe cold wave gripped North India as winter peaked on Tuesday, reducing visibility across Delhi-NCR, Uttar Pradesh and Madhya Pradesh. Transport services were disrupted, while Delhi’s AQI stayed in the very poor category. (Pics/PTI)