The IMD late Friday evening issued a red alert for Mumbai, Raigad and Ratnagiri over the next 24 hours, stating that heavy to very heavy rainfall was likely on Saturday in many places in Palghar, Mumbai, Thane and Raigad districts.
Earlier, IMD said the metropolis and surrounding areas could get intermittent moderate to heavy rain with "possibility of very heavy to extremely heavy rainfall at isolated places" on Saturday.
"For the next 24 hours, that is between July 3 and 4, red alert has been issued for Mumbai, Raigad and Ratnagiri. At some places, there is a possibility of extremely heavy rainfall," an IMD official said late Friday night.
"On July 4, heavy to very heavy rainfall is likely to occur at many places in Palghar, Mumbai, Thane and Raigad districts. At some places extremely heavy rainfall is possible," he added.
According to India Meteorological Department's Mumbai centre, the Colaba weather bureau reported 161.4 mm rainfall between 8:30 am and 8:30 pm on Friday.
During this period, the Santacruz weather station in the city recorded 102.7 mm rainfall.
The IMD had, on Thursday, predicted heavy to very heavy rainfall at isolated places in Mumbai and adjoining coastal districts, and issued an orange alert for Friday and Saturday.
"Mumbai & around rainfall in last 12 hrs at 8.30 pm, shows all pink spots(>40 mm). Most of them towards city & western sub side r more than 100 mm. Widespread hvy & very hvy rains occurred; A much awaited Mumbai Monsoon. More tonight!" KS Hosalikar, Deputy Director General of IMD, Mumbai tweeted in the evening.
The IMD said Harnai weather bureau in coastal Ratnagiri district recorded 30.2 mm rainfall from 8:30 am to 5:30 pm, while Ratnagiri weather station recorded 11.8 mm rainfall during this period.
The Nanded weather bureau, in Marathwada, recorded 20 mm rainfall during the span.