The India Meteorological Department (IMD) on Monday upgraded its existing weather warnings from "orange" alert to "red" alert for Mumbai and surrounding areas.
Maharashtra's Deputy Chief Minister Eknath Shinde has directed authorities to remain alert and provide prompt relief and rescue efforts.
Shinde also appealed to the citizens to follow advisories issued by the authorities and avoid leaving their homes.
Monsoon arrives early
The heavy rainfall comes a day after the IMD announced the onset of monsoon rains in Maharashtra, ten days ahead of the actual date of onset of June 5.
This is the earliest recorded date of the monsoon in Maharashtra since 1990, according to the Indian newspaper The Indian Express.
In Kerala, which is the southernmost Indian state, the monsoon arrived on Saturday, eight days earlier than usual, marking the earliest arrival in 16 years.
The monsoon provides nearly 70% of the rain India requires to recharge its aquifers and reservoirs. The country's farmers highly depend on the annual June-September rains to grow several crops.