Country experiences early monsoon; record May rainfall in Dhaka in 54 years

Monsoon arrived unusually early in Bangladesh this year in the form of a depression entering through Teknaf on 24 May – about eight to 10 days ahead of the typical early June onset. Since then, rains have spread across nearly the entire country, sparing only parts of Rajshahi and Khulna.

A low-pressure system over the sea intensified the impact, causing heavy to very heavy rainfall nationwide, including in Dhaka. The capital recorded 196 millimetres (mm) of rain in the last 24 hours – the highest May rainfall in 54 years, says the met office.

The highest rainfall during this period was recorded in Noakhali with 285mm. Other significant rainfalls included 242mm in Chandpur, 179mm in Cumilla, 164mm in Chattogram, 160mm each in Khepupara and Madaripur, and 141mm in Barishal. 

Waterlogging affected major Dhaka neighbourhoods such as Mirpur and Dhanmondi on Thursday afternoon, with water levels reaching two to four feet and some low-lying areas remaining submerged for more than 24 hours by Friday (30 May).

The Bangladesh Meteorological Department (BMD) has issued a warning for heavy to very heavy rainfall across the country in the next 24 hours starting from 6pm on Thursday. This follows the weakening of a land deep depression into a well-marked low over Sherpur and adjoining Meghalaya.

According to the BMD bulletin, heavy rainfall is defined as 44 to 88mm within 24 hours, while very heavy rainfall exceeds 88mm in the same period. The rain is expected to affect many areas in the Rangpur, Khulna, Barishal, Dhaka, Mymensingh, Chattogram, and Sylhet divisions.

BMD meteorologist Dr Muhammad Abul Kalam Mallik told The Business Standard, "Rainfall this May has been above normal. Usually, a weather system forms over the sea at the end of May, and this year was no exception. However, the rainfall has been heavier, likely because the monsoon is active nationwide. 

"It entered on May 24 and gradually spread from Chattogram and Dhaka to Sylhet. As of Friday, the monsoon is active almost everywhere," he said.

The Meteorological Department notes the last early monsoon arrival on 24 May was in 2009. Typically, monsoon winds enter through Teknaf in early June and spread nationwide by June 10-12.

The summer monsoon is the dominant climate driver in South Asia, caused by intense land heating – especially over India's Madhya Pradesh – creating low pressure that draws moist air from the seas.

Meteorologist Mallik added, "The monsoon influences Bangladesh from early June until mid-October, bringing 70% to 80% of annual rainfall."

Highlighting the record rainfall, he said, "Dhaka's highest single-day rainfall was 341mm on 14 September 2004. However, the 196mm recorded from 6am Thursday to 6am Friday is the highest for May in 54 years. On 25 May 1972, Dhaka had 231mm in one day, but without monsoon winds."

Tackling waterlogging

To address the waterlogging crisis, the local government ministry has set up a control room with officials from Dhaka's two city corporations.

Md Masum, operator of the Kallyanpur water pump run by Dhaka North City Corporation, said, "On Thursday night, water levels exceeded 5 metres, so we started the pump at 9pm. Today, the level dropped to 4.3 metres. Normally, pumps aren't needed before July, but this year, we started nearly two months early."

He added, "When water reaches 5 metres, low-lying houses and roads flood, and water can enter garages. On Thursday, the water level reached 5.3 metres."

Experts argue pumps are intended to pre-emptively drain water by emptying reservoirs when risks arise. But in practice, pumps often activate only after flooding occurs, which is unscientific.

Adil Mohammed Khan, president of the Bangladesh Institute of Planners, told TBS, "There is almost no proactive planning in Dhaka. Action only begins after crises develop, causing prolonged suffering." 

"Despite major spending to clear canals and improve drainage, residents have seen no relief; the problem worsens," he added.

Residents are urged to report waterlogging incidents to the hotlines of Dhaka North and South City Corporations.

Dhaka North City Corporation Administrator Mohammad Ejaz said, "We act immediately once waterlogging is reported. Before this monsoon, we cleared over 100 km of canals in 29 locations. This helped us tackle sudden flooding more effectively. Nearly 200 workers are deployed across 10 zones to manage waterlogging."