The Santacruz weather station gauged a whopping 298 mm of precipitation. This was second only to 346.2 mm of rainfall registered on August 23, 1997, the data showed.
The IMD's Mumbai unit has data on rainfall since 1974.
The figures recorded at the Santacruz weather station in the suburbs represent the overall figure for Mumbai. The department also has a station in Colaba, which is representative of south Mumbai.
"Today's rainfall was extremely heavy. Rains are likely to be heavy tomorrow as well and may abate by late afternoon.
The IMD said the well-marked low pressure area over the Mumbai region is likely to be upgraded to "depression", which would mean more rains.