The rainfall in the 24-hour period before 8.30 am Tuesday was the highest since the July 26, 2005 deluge in Mumbai, officials said.
The rainfall during the 24-hour period was 375.2 mm, the official said, quoting data from the Santa Cruz-based Mumbai Regional Centre of the IMD.
Barring the 2005 flooding of Mumbai, the highest rainfall in a single day in the metropolis was on July 5, 1974. The rainfall recorded by the Santa Cruz observatory on that day was also 375.2 mm.
Rain fury has claimed 27 lives in Maharashtra, including 18 in a wall collapse in Mumbai. The authorities have declared a holiday Tuesday in the city and adjoining regions, asking people to avoid stepping out of their houses.
Eighteen people were killed and over 50 injured in a wall collapse in the northern suburb of Malad in Mumbai early Tuesday following heavy rains.
In Pune, six labourers were killed and three injured after a wall collapsed in Ambegaon area late Monday night. A wall collapse in Kalyan in Thane district early Tuesday killed three people, officials said.