As October draws to a close, Bangladesh would normally begin to experience the first signs of winter.
This year, however, Dhaka and several other parts of the country are still sweltering, with temperatures exceeding 37°C in some areas and mild heatwaves sweeping across several regions over the past two days.
According to the Bangladesh Meteorological Department (BMD), Faridpur recorded the country's highest temperature on Tuesday at 37.5°C, while the lowest was 15.5°C in Tetulia, Panchagarh. Mild heatwaves have affected parts of the country, including Dhaka, Pabna, Sirajganj, Cumilla, Chandpur, Feni, Lakshmipur, Bhola and Barishal.
Temperatures in several areas have been 4–5°C above normal over the past two days.
Meteorologists attribute the unusual heat partly to a low-pressure system over the Bay of Bengal associated with Cyclone Arnab, as well as the possible influence of El Niño, which could contribute to above-normal temperatures this year. Temperatures are expected to gradually ease from Wednesday night.
A heatwave is generally declared when the maximum temperature reaches at least 36°C. Temperatures between 36°C and 37.9°C are classified as a mild heatwave.
Meteorologists say the low-pressure system associated with Cyclone Arnab has contributed to the unusual heat by helping clear skies over many parts of the country, allowing more direct sunlight to reach the Earth's surface. El Niño could also influence temperature patterns this year, although its precise effects will depend on local weather systems and seasonal conditions.
BMD meteorologist Bazlur Rashid told Daily Waadaa that the department had forecast above-normal temperatures this year under the influence of El Niño.
“We have stated in our forecast that temperatures will remain above normal this year under the influence of El Niño. During El Niño, atmospheric circulation and normal weather patterns change. Over the past two days, temperatures in several parts of the country were around 4–5°C above normal,” he said.
Explaining why the heat has felt particularly uncomfortable, Bazlur Rashid said the cyclone and its associated weather systems had contributed to the rise in temperatures.
“Humidity has decreased due to the cyclone and its associated weather system. As a result, people are sweating less and experiencing a burning sensation in their bodies,” he said.
According to the BMD forecast, isolated places across all eight divisions may experience temporary gusty winds, rain or thundershowers in the 24 hours from Wednesday morning. The rainfall could bring a slight drop in temperatures and help ease the heat.
Meteorologists say the effects of a cyclone are not confined to coastal areas. Changes in wind circulation, cloud cover and the position of an associated low-pressure system can also influence weather conditions inland.
According to weather forecasts, extremely severe Cyclone Arnab, which had been positioned over the west-central Bay of Bengal and adjoining areas, crossed the coast of India's Andhra Pradesh.
Mostafa Kamal Palash, a PhD researcher at the School of Environment and Sustainability at the University of Saskatchewan and a climate researcher, said Bangladesh's monsoon officially withdraws around October 15, but the risk of cyclones persists until the first week of December.
“The low-pressure system associated with Cyclone Arnab has recently contributed to rising temperatures in different parts of Bangladesh. Normally, when a low-pressure system develops over the Bay of Bengal, high pressure prevails over the land areas of Bangladesh and India. This clears the skies and allows temperatures to rise,” he said.
Palash said the heatwave could begin to subside from Wednesday night, as rainfall had already occurred in parts of Khulna, with more rain likely in Dhaka and several other areas.
Cloud bands associated with the cyclone could move into Bangladesh through India's Andhra Pradesh, Odisha and West Bengal, potentially bringing rainfall to different parts of the country, he added.
El Niño is the warm phase of the naturally occurring El Niño-Southern Oscillation cycle, a climate pattern that influences weather around the world. It typically occurs every two to seven years, when weakening trade winds allow warmer waters to develop in the eastern Pacific.
El Niño tends to raise global temperatures and disrupt rainfall patterns across large regions, contributing to drought in some areas and heavy rainfall in others.
Extreme heat linked to this year's El Niño could result in more than 600 excess deaths in Bangladesh and over 450,000 deaths globally between June this year and February 2027, according to researchers at the University of Chicago's Climate Impact Lab.
The report, published in late September, said the current El Niño could become one of the strongest on record, potentially triggering floods, droughts, extreme heat and crop losses in different parts of the world.
However, the BMD had earlier forecast below-normal rainfall across Bangladesh from October to December. In September, the country received 17% less rainfall than normal.
The combination of above-normal temperatures and a rainfall deficit has therefore raised concerns about agriculture and everyday life, particularly as farmers prepare for the winter cropping season.