The Meteorology, Climatology and Geophysics Agency (BMKG) predicts that the rainy season – which often brings floods – will begin in late October or early November this year, but several regions have already reported torrential rain during the current transition from the dry to the wet season.

The BMKG has warned of possible extreme weather during the transitional period from September and October in some parts of Indonesia, particularly in West Java. It predicts that heavy rain, lightning and thunderstorms are likely in 24 provinces from Sept. 22 to 24 and in 26 provinces from Sept. 26 to 28.

The agency has asked the public to be on alert for possible flooding, flash floods landslides and whirlwinds that may follow heavy rainfall in the coming days.

On Monday, several parts of Jakarta were inundated following heavy rainfall in the capital and its upstream regions, which saw the Katulampa sluice gate in Bogor, West Java, issue its highest warning level.

The increased water volume at Katulampa on Monday evening prompted Bogor Mayor Bima Arya to ask Jakarta Governor Anies Baswedan in a video call to warn Jakarta residents living near the banks of the Ciliwung River, which flows through Jakarta and West Java, to be on alert in the coming days.

Anies, who later visited the Manggarai sluice gate in Central Jakarta, said the authorities had alerted residents while preparing shelters for affected residents.

“This time, COVID-19 health protocol will be applied at the shelters. We will provide masks; and physical distancing must be implemented,” Anies said, adding that all water gates in the capital were supervised to ensure water from the upstream region could run smoothly.

The Jakarta Disaster Mitigation Agency reported that 49 neighborhood units were still inundated by floodwaters on Tuesday morning. Jakarta reportedly sheltered 104 people affected by floods.

Earlier this year, Jakarta and parts of neighboring Banten and West Java endured massive floods for days due to intense downpours at 377 millimeters per day on New Year’s Eve, the highest level of rainfall in more than a decade. Thousands of people were forced to leave their homes, and multiple deaths were reported.

Despite being much less intense than the rain on New Year’s Eve, the downpours that hammered West Java with 110 mm on Monday have claimed at least two lives, and one person is still missing in the worst-hit city of Sukabumi. At least 210 families in the regency were evacuated and 234 houses were affected, one of which sustained heavy damage, according to the Sukabumi Disaster Mitigation Agency.

Floods also reportedly hit Bogor but details are not available yet.

Jakarta Water Resources Agency head Juaini Yusuf said the agency continued to dredge reservoirs to enlarge the capacity of catchment areas ahead of the rainy season. Work on that project would be carried out in 75 locations across the city by the end of the year.

“In the last rainy season, we saw many spots flooded. Therefore, despite the city cutting its budget for the agency due to COVID-19, we still do our routine activities,” he said while supervising dredging work at the Ria Rio reservoir in East Jakarta on Monday.

In addition to dredging, Jakarta authorities are repairing pumps. The city has 478 stationary pumps in 178 locations and 122 mobile pumps, but Juaini did not reveal how many pumps required immediate repair.

In the coming days, the agency will install more infiltration wells at 200 locations to restore the ability of the ground to hold water, an addition to 2,500 existing wells. It is currently assessing the locations, especially in flood-prone areas.

Juaini said Jakarta was also seeking to acquire land near the rivers of Pesanggrahan, Sunter, Kramat and Angke to start the expansion of river revitalization work as early as next year, as part of its flood control program, which will be partly funded with loans from the central government.

Jakarta has received Rp 4.5 trillion (US$304.48 million) in loans from the central government this year and will use it to pay for new infrastructure to expand flood control measures and for projects related to drinking water and waste management.

West Java Governor Ridwan Kamil, meanwhile, said he had instructed regional leaders under his jurisdiction to prepare measures to anticipate floods and landslides.

“The West Java administration, through its public works agency, launched projects to anticipate floods over the past two weeks. Hopefully, [the projects] will be effective,” he said on Tuesday without elaborating.

Bogor Mayor Bima Arya warned his residents near Ciliwung River to be on alert, with 13 of the city’s subdistricts located adjacent to the river.

In West Kalimantan, the Kapuas Hulu administration has declared a 14-day state of emergency in response to massive flooding that damaged at least 980 homes in the region on Sunday. The state of emergency was declared on Monday and is expected to end on Sept. 27. No fatalities were reported, but the disaster has forced residents to abandon their homes and seek shelter on higher ground.

-- Tri Indah Oktavianti, Moch. Fiqih Prawira Adjie and Arya Dipa contributed to the story.