Why was the heat less intense this April?

“My body feels like it’s burning under this scorching sun. Still, I keep working hard just to earn some money. But I’m afraid I might come down with a fever again.”

Agricultural labourer Ratan Ali said this while working in the fields. No, he didn’t say it about the heat this year. He shared those words in a report published in Prothom Alo on 30 April 2024, describing the severe heat he was enduring.

The report was titled, Chuadanga records highest temperature in 40 Years: 43.7°C. At the time, Ratan was working in the Hajrahati fields in Chuadanga Sadar Upazila.

Last April, stories of extreme heat - where people said they felt like their bodies were burning - were widespread in the media. Reports came in from all corners of the country. And it wasn’t just workers like Ratan who were affected - teachers, physicians, students, engineers, and day labourers from various professions shared their suffering.

Temperature records were being broken one after another. The official data confirmed it, and in reality, day-to-day life had become unbearable. In fact, it was the hottest April in Bangladesh’s 76-year history.

After a 26-day break for Ramadan last year, educational institutions were scheduled to reopen on 21 April. However, just a day before that, the holiday was extended until 27 April. This decision came immediately after the Meteorological Department issued a “red alert” due to extreme heat.

But this year, the situation during April - the hottest month in Bangladesh - is noticeably different. Why is that?

April is typically the hottest month in Bangladesh, with an average temperature of 33.2°C. May follows closely, with an average high of 32.9°C.

However, unlike last April’s intense heat, this year has been milder. The average temperature in April this year was 3°C lower than that of April last year.

According to meteorologist Md Bazlur Rashid of the Bangladesh Meteorological Department, “This year, the average temperature in April was 33.8°C, while last year’s dreadful April had an average of 36.3°C.”

In Bangladesh, a temperature range of 36°C to 37.9°C is considered a mild heatwave. A range of 38°C to 39.9°C is classified as a moderate heatwave. When temperatures reach 40°C to 41.9°C, it is labeled a severe heatwave. Anything above 42°C is deemed an extreme heatwave.

Taking into account the criteria for heatwaves, it can be said that last year, every single day in April experienced heatwaves across the country.

And that’s not all - on 20 out of 30 days in April 2024, the highest recorded temperatures exceeded 40°C. Between 13 and 30 April, the temperature remained above 40°C continuously. The highest temperature was recorded on 30 April: a scorching 43.8°C.

Muhammad Abul Kalam Mallik, a meteorologist at the Bangladesh Meteorological Department who has long studied heatwaves, told Prothom Alo on 25 April 2024, “After analysing data since 1948, I found no other instance of such a prolonged heatwave. You could say it broke a 76-year record.”

In contrast, this year the maximum temperature reached close to 40°C in only one day. On 23 April, the highest temperature recorded in the country was 39.8°C.

According to data on heatwaves from 1981 to 2023 stored by the Meteorological Department, Rajshahi experienced the highest number of heatwave days in April 2010 - with 20 days of mild to severe heatwaves.

No other month has recorded so many consecutive days of heatwaves. Over the last 43 years, Jashore has recorded the highest number of heatwave days, followed by Dhaka and Chuadanga.

Last year’s heatwave lasted an uninterrupted 35 days, setting a new national record.

Global wind patterns, climate conditions, and atmospheric behaviour over the subcontinent all play a role in temperature increases or decreases.

It is now widely understood that the Earth is warming. Almost every month of last year broke previous heat records. Up to March this year, global temperatures also remained above historical averages.

Why was April 2024 so intensely hot? Globally, the average temperature rose by 1.3°C last year, and Bangladesh felt the impact as well.

El Nino is a climate phenomenon involving changes in wind and sea surface temperatures in the central and eastern Pacific Ocean. It usually signals a warming trend. Its opposite, La Nia, indicates cooling.

El Nio activity was first observed in September 2023, and experts warned early on that it could lead to intensified global heatwaves in 2024. Australia’s Bureau of Meteorology confirmed El Nio conditions. In a report on 16 April, they announced that El Nio had officially ended.

Professor AKM Saiful Islam, Director of the Institute of Water and Flood Management at the Bangladesh University of Engineering and Technology (BUET), explained to Prothom Alo last year that although El Nino had officially ended, its lingering effects contributed to the extended heatwaves.

Meteorologists had already predicted that this year would not be as dangerously hot as last year, due to changes in global atmospheric conditions.

This year, La Nina conditions were expected to dominate, which naturally led to the assumption that extreme heat might not occur.

On Monday (5 May), AKM Saiful Islam said that currently, both El Nino and La Nina are in a neutral state. This is likely why April was not as hot as last year. Even now, nearly a week into May, temperatures are still not as extreme as they were at this time last year.

Kalbaishakhi (nor’wester) storms help to ease the summer heat. These storms bring heavy rain, which, even if only for a few days, reduces the temperature before it rises again.

Last year’s unusually long and intense heatwaves in April and May were largely due to the very low number of Kalbaishakhi storms. Typically, Bangladesh experiences around nine Kalbaishakhis in April and 13 in May. However, last year there were only two such storms in April and four in May, according to senior meteorologist Muhammad Abul Kalam Mallik of the BMD.

Muhammad Abul Kalam Mallik has long studied temperature patterns and thunderstorms.

This year, there have been at least nine Kalbaishakhi storms in April, said Mallik. While rainfall in April was slightly below average this year, it was still more than in April of last year. Intermittent rain occurred throughout the month in Dhaka and other parts of the country.

Nayla Islam, a woman in her fifties who works a full-time job and is a mother of two school- and college-going children, still recalls the “terrible” heat of April last year.

Thinking of those days, she bought an air conditioner this year for her home in Tejkunipara, Dhaka. “It was a stretch financially, but I bought the AC for the sake of my children. But April turned out to be quite pleasant this year. I’m not sure how May will be. I think we used the AC only for three days in April,” she said.

Many others, too, found this April to be a welcome relief from the heat.

Meteorologist Md Bazlur Rashid noted that rainfall in Bangladesh from November last year to March this year was extremely low - among the lowest since 2013. 

This five-month dry spell was primarily due to the absence of western low-pressure systems, which typically cause rainfall during this period.

However, in April, the pace of the westerly wind flow increased, leading to more rainfall.

Md Bazlur Rashid explained, “In April, the western low-pressure systems became more active, which led to more rain. As a result, the heat was significantly reduced this time.”