Back-to-back low pressure triggered intermittent spells of light to moderate rain last month, giving the first month of monsoon, June, its typical feel, which was missing from Junes in the past few years.
Last month saw the formation of three low pressures and witnessed full impact of another one that formed at the end of May and moved onto land as soon as June began. The Bangladesh Meteorological Department already confirmed that the onset of the ongoing monsoon was the earliest ever in over four decades.
There was only one low pressure formed in June last year, in the third week of the month. Last year鈥檚 June brought scorching heat and triggered draught-like situation for the first three weeks, visited by frequent heatwaves. The June last year ended with 9 per cent rain deficiency, witnessing the highest maximum temperature of the month exceeding 1.7C above normal while the lowest minimum temperature was 1.3C higher.
In 2023, June looked even more unfamiliar as a monsoon month as it ended with 16 per cent rain deficiency with the highest maximum temperature of 41.5C recorded in Rajshahi. The June of 2023 coincided with the longest-ever heatwave stretching over more than one month. Many days of that month endured the maximum temperature past 40C with the highest maximum temperature go past 1.7C above normal. The lowest minimum temperature was also 0.6C higher than normal. A severe drought broke out, leaving farmers in severe water crisis across Bangladesh, pushing people to gather in special prayers for rain.
The latest June, although it experienced 19.3 per cent less rainfall than normal, the lack of rain did not cause the temperature to soar. It is because the rain was well distributed over the month, not leaving a long period without any rain.
In the latest June, of the eight divisions, except Barishal and Khulna, all divisions witnessed less than normal rain. The highest rain deficiency of 49 per cent was recorded in Sylhet, followed by Dhaka recording 33 per cent less rain.
The result of frequent rainfall was that heatwave was very weak. There were only four days of heatwave in three phases in the first two weeks of the month. The heatwave occurred in northern, south-western and parts of coastal areas and retreated immediately after their occurrence. A heatwave occurs when the temperature reaches 36C or goes beyond the threshold. The highest maximum temperature in the month was 0.5C above normal, while the lowest minimum temperature was 0.3C above normal.
The highest maximum temperature of 38.8C was recorded in Dimla in Nilphamari on June 14. Days of June, however, felt very hot due to very high moisture in the air. Rain events were also mostly light, not enough to keep the temperature low for long. Day temperatures mostly remained around 35C.
The latest BMD forecast said that the ongoing wet spell of light to moderate rain would continue over the next 10 days, leaving almost no chance of any heatwave setting in.
On Friday, the country鈥檚 highest maximum temperature of 34C was recorded in Sylhet, Rangpur and Dimla. In the 24 hours until 6:00pm on Friday, Bangladesh鈥檚 highest maximum rainfall of 162mm was recorded in Cox鈥檚 Bazar.
According to the BMD鈥檚 Changing Climate of Bangladesh report released last year, heatwaves are most frequent during the pre-monsoon months, though they are not rare during monsoon. The report, covering the timeline between 1980 and 2023, notes a rise in heatwave days in monsoon across Bangladesh.
It notes that particularly in June, heatwaves have become more frequent in Rajshahi, Rangpur, Khulna and Sylhet. Heatwave frequency during monsoon substantially increased after 2000, the report reveals.
Hot days rising in monsoon could be an indication of the season, accounting for 80 per cent of annual rainfall, getting drier, potentially losing its precipitation capacity, which is essential for the country鈥檚 agriculture and economy.