One day it rains, the next day intense heat returns. At times, Sylhet faces prolonged rainfall, while sudden dry spells disrupt the seasonal cycle. Over the past few years, climate change has altered the region’s temperature and rainfall patterns, affecting its haors, soil and agriculture.
Experts blame unplanned land use, rapid urbanisation and excessive economic activities for disturbing nature’s balance. They say major changes in land use over the past three decades have weakened Sylhet’s ecosystem and its ability to withstand climate extremes.
According to the Bangladesh Meteorological Department, Sylhet’s average maximum temperature has increased by nearly 5 degrees Celsius in two decades. Between 2001 and 2005, the average maximum temperature was 33.16 degrees Celsius, which rose to around 38.22 degrees Celsius between 2020 and 2025.
Rainfall has increased as well. The average annual rainfall rose from 3,808 millimetres between 2001 and 2005 to 4,627 millimetres between 2020 and 2025.
The timing of rainfall has also changed. Although June, July and August are considered the peak monsoon months, heavy rainfall is increasingly occurring before the season begins.
This year, Sylhet recorded 1,840 millimetres of rainfall during the pre-monsoon period, followed by 1,774 millimetres in June and July. In total, the region received 3,614 millimetres of rainfall in the first five months of the year.
With rivers already swollen, further rainfall in Sylhet and neighbouring Meghalaya could trigger flooding, according to weather officials.
Sylhet turns into a ‘heat island’
Experts say Sylhet city is increasingly becoming a “heat island” due to rising temperatures, declining vegetation and rapid urban expansion.
Md Anwarul Islam, associate professor of the Department of Geography and Environment at Shahjalal University of Science and Technology, said wetlands and trees once absorbed heat, but their destruction has altered the local climate.
“Sunlight falling on the earth’s surface is absorbed by wetlands and vegetation. But as wetlands are destroyed and trees are cut down, the heat is directly reflected back, warming the air,” he said.
Anwarul, who is specializes in regional climate systems, climate vulnerability, and natural disasters, said cities, including Sylhet, now lack natural spaces to absorb heat.
“Tall buildings and air-conditioner outlets in urban areas are keeping temperatures constantly high,” he told TIMES of Bangladesh, blaming unplanned development for worsening the situation.
Over the past 30 years, land use in haor areas has changed significantly, Anwarul said, regretting that in the name of protecting haors, embankments have divided water bodies into smaller sections while unplanned bridges, roads and protection projects have also changed land use patterns.
He added that indiscriminate tree cutting and increased houseboat activity had damaged the haor ecosystem.
Rainfall pattern shifting
Sylhet’s rainfall has increased significantly over the past two decades. The region recorded 3,474 millimetres of rainfall in 2001, compared with 8,209 millimetres in 2024.
An analysis of rainfall data shows that precipitation has increased not only during the monsoon but also during the pre-monsoon period.
Between 2001 and 2005, average pre-monsoon rainfall from March to May was 1,720 millimetres. Between 2020 and 2025, it increased to 2,957 millimetres.
Anwarul said Sylhet’s rainfall is influenced by north-eastern monsoon winds carrying moisture from the Bay of Bengal.
“The sea surface absorbs large amounts of sunlight during March and April and releases water vapour. These vapours are carried by winds and cause rainfall here. As the monsoon arrives earlier, Sylhet is experiencing early rainfall,” he said.
Excess rainfall damages soil
Increasing rainfall and repeated floods are affecting Sylhet’s soil quality, raising acidity and reducing nutrients.
Researchers say 92 per cent of Sylhet’s soil is acidic, while 26 per cent is highly acidic. Around 66 per cent of soil has a pH level between 4.5 and 5.5, while only 8 per cent has a pH level between 5.6 and 6.5.
A comparison of Soil Resource Development Institute studies from 2005 and 2026 shows that soil acidity is increasing in several areas.
At the same time, important nutrients, including organic matter, nitrogen, phosphorus, potassium, magnesium, calcium and sulphur, are declining.
Mohammad Kamal Hossain, chief scientific officer of the Soil Resource Development Institute in Sylhet, said excessive rainfall and upstream water flows are accelerating soil erosion.
“Calcium and magnesium, among other elements, are declining rapidly. As soil quality deteriorates, cultivation patterns are changing,” he said.
He also blamed excessive use of urea fertiliser for increasing soil acidity.
“Nearly 80 per cent of Sylhet’s soil has a pH level between 4.5 and 5.5. Low pH soil is suitable for citrus fruits,” he said.
Around 75 per cent of Sylhet consists of haor areas, which remain underwater for much of the year. While acidic soil does not create major problems for rice cultivation, it poses challenges for fruit and vegetable production.
Climate change reshapes farming
Traditionally, Sylhet’s acidic soil has been considered ideal for citrus fruits. However, climate change, improved technology and orchard expansion are reshaping farming patterns.
Mango and jackfruit production has now surpassed citrus fruits such as oranges and lemons in Sylhet division.
Despite increased production, mango and jackfruit have yet to make a major economic impact, as the region still depends heavily on supplies from Rajshahi, Chapainawabganj and Tangail.
Experts say Sylhet’s soil remains naturally suitable for citrus fruits, while its hilly terrain favours jackfruit cultivation.
Md Rakibul Islam Ruman, a horticulturist at the Horticulture Centre in Khadimnagar, said acidic soil makes Sylhet suitable for lemons, oranges and Malta.
“Pineapple cultivation is also expanding in Golapganj and Fenchuganj. Mango, jackfruit and watermelon can be grown, but lime must first be applied to neutralise the soil,” he said.
Professor Mohammad Shahidul Islam, dean of the Faculty of Agriculture at Sylhet Agricultural University, said low soil pH does not prevent the cultivation of other fruits.
“However, climate change is affecting fruit production. Excessive rainfall and fog increase diseases and pest attacks, damaging mango and other crops,” he said.
He added that soil conditions vary widely across Sylhet. “With proper soil management, all kinds of fruits can be produced. However, Malta, guava and citrus fruits remain more suitable for this soil.”
