Kathmandu, June 20 The Meteorological Forecasting Division officially declared the onset of monsoon in Nepal today, after a delay of 10 days from the normal date. Monsoon usually enters Nepal on June 10 and withdraws on September 23. Last year, the country welcomed monsoon on June 8, two days ahead of the normal date. “Monsoon has entered Nepal after a delay of 10 days from the eastern region of the country and is in the process of gradually advancing towards the western region. “It may take a few days for the active monsoon to spread across the country bringing plenty of rain,” read a special weather bulletin issued by the MFD. The period of four months between June and September is generally called the South Asian Monsoon in Nepal. Once monsoon enters from the eastern region, it makes westward advancement through the central region to the remaining parts of the country, in a few days. Monsoon lasts for an average of 105 days. “Nepal receives 80 per cent of annual rainfall on an average during the monsoon, which originates in the Bay of Bengal and moves along the southern flanks of the Himalayas. The average annual rainfall in Nepal is 1,600 mm but it varies from place to place, depending on climatic conditions,” read the bulletin. The period between June and September is called southwest monsoon season. “As per the forecast of the14th session of South Asian Climate Outlook Forum held in Kathmandu on April 18-23, below-normal rainfall is likely to occur in western parts of Provinces 1, 2, 3 and 5. Gandaki, Karnali and Sudurpaschim provinces will receive normal rainfall,” the bulletin stated. SASCOF had developed a consensus outlook through an assessment of experts on the prevailing global climate conditions and forecasts from different climate models around the world. Currently, weak El Niño conditions are prevailing over the Pacific Ocean and there is strong consensus among experts about the possibility of further weakening of these conditions during the latter phase of the monsoon season, SASCOF said in its report.