Why does the heat persist even though its rains every day?

Zahur Hossain wiped the sweat from his brow as he stood at the Farmgate metro station waiting for his train to Motijheel. Despite the short distance from his home, he took a rickshaw to get there. Even that short journey left him drenched in sweat.

"The moment I step outside, I start sweating. It''s raining, but there''s no sign of the heat letting up," he said.

Many people in Dhaka share Zahur''s experience. But it is not only those out on the streets who are suffering. People staying indoors, whether cooking, doing household chores or carrying out other daily activities, are also struggling with the oppressive heat.

For the past few days, Dhaka and much of Bangladesh have seen an erratic alternating of sun and clouds. Intermittent rain fell on Sunday morning, leaving the sky overcast by 11:00 am. Yet, instead of bringing relief, the rain has only intensified the muggy, uncomfortable atmosphere.

Rain would normally bring relief from the heat. Meteorologists, however, say several factors are preventing that from happening. These include latent heat released after rainfall, excessive moisture in the air, the monsoon not yet in full swing and the continued inflow of humid air from the south.

Muhammad Abul Kalam Mallik, a senior meteorologist at the Bangladesh Meteorological Department, told Prothom Alo that even after rainfall, the Earth''s surface is not cooling quickly. Instead, heat stored in the ground and urban concrete structures builds up again after the rain.
As a result, latent heat is released into the atmosphere, making the environment feel warmer.

He added that the amount of water vapour currently present in the air is unusually high. This prevents sweat from evaporating easily from the human body, making temperatures feel hotter than they actually are.

The clouds that form during the monsoon season are generally located close to the Earth's surface. Rain from these clouds does not provide immediate relief. Mallik said prolonged rainfall would bring greater comfort but such continuous rain has yet to occur.

While the monsoon entered Bangladesh about a week later than usual this month and has now spread across the country, it remains weak.
Meteorologist Kazi Zebunnesa said the monsoon has expanded nationwide but has not yet become fully active. As a result, the country is not experiencing sustained and sufficient rainfall.

At the same time, large volumes of humid air are entering Bangladesh from the south and across the Bay of Bengal. This is increasing the amount of moisture in the atmosphere and contributing significantly to the muggy conditions.

She added that a western low-pressure area currently persists over the southwestern region near the Sundarbans. As a result, humidity levels remain particularly high there, making conditions feel even more uncomfortable.

Meteorologists say much of the rain currently falling across the country is brief and scattered. Rainwater therefore evaporates quickly and returns to the atmosphere, further increasing humidity. At the same time, the lack of widespread, long-lasting rainfall means environmental temperatures are not dropping significantly.

According to weather experts, meaningful relief is likely only if the monsoon becomes more active and brings moderate to heavy rainfall across most parts of the country for several consecutive days. Until then, the alternating pattern of sunshine and rain is expected to keep the humid heat in place.

The Bangladesh Meteorological Department has already forecast that rainfall during this year's monsoon season may be below normal, while temperatures could remain higher than usual.

On Saturday, the country's highest temperature was recorded in Ishwardi, Pabna, at 36.7 degrees Celsius.