Dharamsala /Gorakhpur/Lucknow, Jan 09 (ANI): Dense fog reduced visibility even as biting cold has jammed life in parts of northern India on Thursday. A blanket of thick fog enveloping northern India hit rail traffic with dozens of trains running behind schedule or cancelled. The visibility dropped below 100 metres. Meanwhile, the mercury dropped to freezing point in Dharamsala, leading to formation of frost on plants. People were seen sitting around bonfires on pavements in Gorakhpur. Commuters at a railway station also complained of delays, affecting their day-to-day life. Meanwhile, authorities in Uttar Pradesh also introduced night shelters ‘Raain Basera’ for poor people.