Delhi woke up in a thick blanket of dense fog on Wednesday morning. The national capital recorded a minimum temperature of seven degrees. Dense fog reduced visibility in the NCR and affected the train traffic. At least 20 trains were running late due to low visibility in the Northern Railway region, ANI reported. Dense fog was also reported from Punjab, Haryana, West Rajasthan and East Uttar Pradesh. Weather experts said cold northwesterly winds will start blowing from Wednesday onwards, leading to a dip in temperatures.