The IMD on Saturday declared the arrival of southwest monsoon over Mumbai. June 11, also marked the official onset date. The onset of monsoon was declared on Saturday after a night of significant thunder & lightning activity. The rainfall recorded in the 24 hours ending 8.30am on Saturday by the IMD Colaba observatory was 61.8 mm & Santa Cruz observatory was 41.3 mm. As per IMD rainfall categorisation this falls in moderate rain category (15.6mm up to 64.4mm). After remaining dry since the beginning of the month, the city started receiving pre monsoon showers from Thursday evening itself. This had also lead to localised water logging in some areas. Weather officials said that monsoons had advanced over most parts of Konkan including Mumbai and some parts of Madhya Maharashtra.