Kathmandu, September 29 Though low pressure has considerably weakened over a period of past one week, it is likely to take one more week for official declaration of monsoon withdrawal. According to Department of Hydrology and Meteorology, the official withdrawal of monsoon could be declared Tuesday onwards despite that fact that it has already started to show signs of weakening with reduced rainfall. The DHM had officially declared the onset of monsoon on June 8, two days ahead of the normal date this year. Monsoon usually enters Nepal on June 10 and withdraws on September 23. DHM said monsoon is believed to have been retreated only after the westerly winds replace the easterly winds. Monsoon rains have started withdrawing from India and Pakistan as well. The delay in monsoon retreat has been blamed on depression over the Bay of Bengal two weeks ago. When there is considerable reduction in moisture content as shown by satellite images and no possibility of rainfall continuously for some days, it can be termed as the sign of withdrawal of monsoon, DHM officials informed. Monsoon lasts for an average of 105 days. Nepal receives an average of 80 per cent annual rainfall during the monsoon.