Metropolitan Municipality has warned the residents of the city to be prepared for a heavy summer rainfall that is expected to start on Saturday morning.The statement released by the municipality on late Friday said that it predicted that between 51 and 75 kilograms of rain might fall in Istanbul per square meter during 15-minute periods of rain. The officials also said the rainfall may lead to traffic congestion, flooding in several district in the city and added that the Fire Departments, Road Maintanance and other units within the municipality have taken precautions to deal with potential crises led by the Disaster Coordination Centre (AKOM) and others.