The BMD defines a heatwave based on actual air temperature, counting it when the daily maximum reaches at least 36°C for two or more consecutive days. On the other hand, the Heat Index or apparent temperature used by the Climate Change Knowledge Portal combines air temperature and humidity to estimate how hot it actually feels.
In 2025, heatwaves spread even further, reaching as many as 49 districts at once. The situation was most severe in 2024, when heatwaves affected 51 out of the 64 districts and set a record for the number of heatwave days in April alone.
Recent data from the Bangladesh Meteorological Department (BMD) also show how intense and widespread this heat has become. Already this year, heatwaves have affected up to 40 districts on a single day (June 2), while smaller spells earlier in the season covered around a dozen districts.
The Heat Index (HI) or apparent temperature, which combines air temperature and humidity to estimate how hot it actually feels, is increasingly used by scientists and health researchers to assess the true burden of heat on the human body. Scientists and researchers associate heat index over 35°C with health risks, infrastructure stress and reduced labour productivity.
The findings are based on an analysis by The Daily Star using Heat Index (HI) data compiled by the World Bank’s Climate Change Knowledge Portal and heat-related health data from the Lancet Countdown.
This level of heat is not just uncomfortable. At this threshold, the human body struggles to cool itself, especially in Bangladesh’s humid conditions. This increases the risk of illness, reduces people’s ability to work, and puts pressure on the economy.
No country in the world, except for Cambodia, experienced a steeper rise in the number of such days over the same period.
The number of days each year when the heat feels unsafe for the human body has nearly tripled in the past two decades. In 2000, Bangladesh recorded about 46 days when the “feels-like” or apparent temperature crossed 35°C. By 2024, that number rose to 120 days -- an increase of 163 percent. .
Bangladesh is warming at a pace never seen before, and the rising heat is becoming increasingly dangerous.
How the same air temperature feels at different levels of humidity
60 percent of the heatwaves recorded in Bangladesh between 2020 and 2024 would not have occurred without climate change.
Extreme heat has become normal since the 2010s . Compared to the previous decade, the number of such annual days saw a 49.2% increase. Most research attributes this shift to human-caused climate change.
Bangladesh's heat is amplified by extreme humidity . When moisture-laden air prevents sweat from evaporating, the body's natural cooling mechanism fails, pushing the apparent temperature far above the actual reading of dry temperature. On the worst days in Dhaka, a 35°C reading can feel closer to 45°C.
Bangladesh ranked fourth in the world in 2024 for the number of days with a heat index above 35°C. Only Bahrain, Qatar and the United Arab Emirates — all desert Gulf states — were ahead.
Although Bangladesh has long been hotter and more humid than many parts of the world, such conditions were
generally manageable in the past. However, the situation has worsened over the past 15 years, with extreme
heat days becoming increasingly frequent and hazardous.
From 2010-2024, Bangladesh on average experienced 96 days a year when the apparent temperature exceeded 35°C.
A long-term review of climate data also shows an alarming upward trend.
In the 1950s, Bangladesh experienced fewer than 30 days per year on average when the heat index crossed 35°C.
That number has steadily increased each decade, nearly quadrupling over time.
It accelerated sharply in the 2010s, which saw nearly 300 additional days above this threshold compared to
the previous decade. This spike continued in the 2020s.
Annual days with a heat index above 35°C, by division, 1950–2024. Press play or drag the
slider to watch the heat spread.
1950
1970
1990
2010
2024
1950
Nat. avg
16
daysFewer heat days
More
0 → 150+ days / year
Source: ERA5 Reanalysis 0.25 Grid. Climate Change Knowledge Portal.
World Bank Group. Annual count of days with a heat index above 35°C, summed across April–September.
Regional patterns also show how widespread the change has become. Khulna has consistently been the hottest
division, with heat days rising from around 51 days per year in the 1950s to about 132 days in the 2020s.
Chattogram, historically the least affected, still records fewer heat days than other divisions, but it now
experiences more extreme heat than the hottest regions did in earlier decades.
Md Rabiul Awal, chairman of the Department of Meteorology at Dhaka University, attributed this rise in
extreme heat to global warming. “According to most climate projection models, this trend is expected to
continue in the coming decades,” he told The Daily Star yesterday.
According to Lancet Countdown data, more than 4 out of every 1,000 deaths in Bangladesh between 2010 and 2021
were linked to heat exposure, an increase of 33 percent from the previous 12-year period.
Per 1000 deaths in Bangladesh
6.0
4.0
2.0
0.0
1990
1.2%
of deaths
1991
2.3%
of deaths
1992
4.5%
of deaths
1993
1.1%
of deaths
1994
2.9%
of deaths
1995
4.6%
of deaths
1996
3.7%
of deaths
1997
1.7%
of deaths
1998
3.7%
of deaths
1999
3.5%
of deaths
2000
2.3%
of deaths
2001
1.9%
of deaths
2002
1.1%
of deaths
2003
2.5%
of deaths
2004
2.6%
of deaths
2005
3.9%
of deaths
2006
3.8%
of deaths
2007
3.6%
of deaths
2008
3.3%
of deaths
2009
5.0%
of deaths
2010
5.7%
of deaths
2011
2.0%
of deaths
2012
4.6%
of deaths
2013
3.0%
of deaths
2014
5.7%
of deaths
2015
3.1%
of deaths
2016
4.0%
of deaths
2017
3.1%
of deaths
2018
3.2%
of deaths
2019
5.7%
of deaths
2020
4.8%
of deaths
2021
5.1%
of deaths
1990
2000
2010
2021
Methodology
This indicator monitors heat-related mortality using a newly-developed model framework that builds on a mortality database for 120 countries. It applies state-of-the-art meta-prediction models to estimate the association between temperature and mortality from all causes globally, combined with yearly mortality estimates from the Global Burden of Disease — making it the most comprehensive global estimate of heat-related mortality yet.
Older people are particularly vulnerable. Around 1,430 people aged 65 and above died from heat-related causes
in Bangladesh between 2017 and 2021, according to a
2023 study by the Grantham Research Institute on Climate Change of London School of Economics.
Extreme heat causes heatstroke and exhaustion and worsens existing conditions such as heart disease,
diabetes, and asthma. It also limits outdoor activities. In 2024, an average person in Bangladesh would have
been exposed to extreme heat stress for about 5.2 hours per day while outdoors. Only Cambodia fared worse in
this indicator.
In 2024, an average person in Bangladesh would have been exposed to extreme heat stress for about
5.2 hours per day while outdoors. Only Cambodia fared worse in this indicator.
A nationally representative
World Bank survey in 2024 also found that the likelihood of depression increased by 23.8 percent
and anxiety by 37.1 percent on days when temperatures exceeded 35°C. Women were more affected.
Extreme heat also hurts the economy. In 2024 alone, heat-related physical and mental health impacts resulted
in an estimated loss of up to 25 million workdays in Bangladesh. The economic cost is estimated at between
$1.33 billion and $1.78 billion, or roughly 0.3 to 0.4 percent of the country’s GDP, the same WB study
found.
Much of this loss comes from reduced labour productivity. According to Lancet Countdown estimates, an average
worker in Bangladesh lost about 391 working hours in 2024 due to heat stress. Between 2015 and 2024, only 10
countries recorded higher annual work-hour losses.
$1.33B – $1.78B
Annual economic losses (2024)
Equivalent to roughly 0.3 percent to 0.4 percent of Bangladesh's Gross Domestic Product (GDP).
391 hours
Average lost time per worker (2024)
The standard annual working hours lost per individual worker due to heat exposure.
Agricultural workers were the most affected, losing an average of 732 working hours in 2024 due to extreme
heat, the equivalent of around 92 full working days, based on an eight-hour workday. Construction workers
lost about 285 hours, while service-sector workers lost around 111 hours.
For many workers who depend on daily wages, this translates directly into lost income. For example, assuming
a daily wage of Tk 500 for a farm worker, losing 92 working days would mean a loss of around Tk 46,000 in a
single year or about Tk 4,000 per month.
In a country where millions rely on daily earnings to survive, such losses can have serious consequences for
household income and food security.
The Daily Star spoke to four rickshaw pullers aged 50-65 in Dhaka’s Farmgate. All four said they lose working
hours during extreme heat, as the conditions make it difficult to carry passengers.
Md Azad, one of the rickshaw pullers interviewed, said that due to the heat, he has to rest a while after
every trip. “On very hot days, I earn Tk 200-300 less.”
Climate projections show Bangladesh will face even more days with heat index above 35°C in the coming
decades.
Between 2026 and 2050, the country could see an additional 32 such days each year under a moderate,
“middle-of-the-road” climate scenario. This scenario is based on the assumption that socio-economic
development and greenhouse gas emissions will continue along historical trends until around mid-century
before a gradual decline.
Even in the best-case scenario, where the world reaches net-zero emissions by 2050, Bangladesh is likely to
face at least 23 extra days annually.
In the worst-case scenario, where fossil fuel use remains high, the increase could reach 41 additional days.
Average annual days with HI>35°C across key timeline.
Shared Socioeconomic Pathways
Source: ERA5 Reanalysis 0.25 Grid. Climate Change Knowledge Portal.
World Bank Group
Coastal regions are expected to be hit the hardest. For example, Khulna is projected to remain the most
heat-affected area until around mid-century, after which Barishal could overtake it. By the 2080s, both
divisions may face nearly 200 days of extreme heat each year even in the middle-of-the-road scenario.
This growing intensity is driven not just by rising temperatures, but by humidity. In Khulna and Barishal,
increasing moisture levels significantly raise the “apparent” temperature, making heat more dangerous.
By the end of the century, humidity is expected to become the region’s dominant climate stressor, increasing
discomfort and risk in these already waterlogged, riverine landscapes.
Annual days with a heat index exceeding 35°C by division.
Scenario Definition
SSP245 (Shared Socioeconomic Pathway 2-4.5): Represents a middle-of-the-roadRepresents a middle-of-the-road scenario where societal and economic trends follow historical patterns. Greenhouse gas emissions plateau around 2050 before declining, leading to an estimated global warming stabilisation threshold of roughly 2.7°C by the year 2100.
Source: ERA5 Reanalysis 0.25 Grid. Climate Change Knowledge Portal.
World Bank Group
According to Lancet Countdown, climate change was responsible for 51 out of 86 heatwaves recorded in
Bangladesh between 2020 and 2024. While climate change is identified as the primary driver of extreme heat
in Bangladesh, experts and a growing body of research point out that local factors also play a role.
For example, rapid urbanisation is increasing heat exposure, especially in cities like Dhaka. Concrete
buildings, roads, and infrastructure trap heat, create what is known as the Urban Heat Island effect. This
causes cities to become significantly hotter than surrounding rural areas.
Bangladesh is also losing tree cover at a faster rate than before.
Between 2001 and 2024, the country lost an average of 10,906 hectares of forest each year, according to
satellite data from Global Forest Watch, which tracks canopy cover at a 30% density threshold. The annual
loss has increased over time -- from about 4,394 hectares in the 2000s to over 17,000 hectares in the 2020s.
Comparing annual tree cover loss (ha) with days experiencing a Heat Index over 35°C in
Bangladesh.
Source: Global Forest Watch
While deforestation does not immediately raise temperatures in a single year, long-term loss of tree cover
reduces a country’s natural cooling capacity, which makes heat more intense over time.
×
Golam Rabbani, director of the Centre for Climate Change and Environmental Research at BRAC University, said
that temperature levels tend to rise with increasing human and industrial activity.
“Urbanisation undoubtedly influences local temperatures. Expanding industrial operations, growing vehicle
use, dense construction, and rising population concentrations all contribute additional heat to the urban
environment,” he told this newspaper yesterday.
As the intensity of these activities varies across different parts of the city, temperature readings can also
differ between areas such as Sher-e-Bangla Nagar, Farmgate, and Jatrabari, he said.
“Deforestation also contributes to extreme heat by reducing evapotranspiration -- the natural process through
which trees and vegetation release moisture into the atmosphere, helping cool the surrounding environment.
As green cover declines, this cooling effect weakens, increasing the risk of higher temperatures,” he said.
