The India Meteorological Department (IMD) on Friday issued a red alert for Mumbai for Saturday and Sunday, forecasting heavy to very heavy rainfall at a few places with extremely heavy rainfall at isolated locations, civic officials said.A red alert was also issued for the neighbouring Thane, Palghar and Raigad districts.Mumbai has been battered by rains throughout this week following the late onset of the monsoon, throwing normal life out of gear.As per the IMD's district-wise forecast issued on Friday afternoon, the city is likely to receive heavy to very heavy rainfall at a few places with isolated extremely heavy spells on July 4 and 5.The probability of the forecast was categorised as "very likely".The IMD also forecast heavy to very heavy rainfall at isolated places in Mumbai on Monday, while heavy rainfall is likely at a few places on Tuesday. As per BMC officials, neighbouring Thane and Palghar districts have also been placed under a red alert for Saturday and Sunday, with a forecast of extremely heavy rainfall at isolated places. A red alert has also been sounded for neighbouring Raigad district for Friday and Saturday.