News desk: Rains are falling in various parts of Bangladesh since the beginning of October. However, the Meteorological Department has said that the country may receive less rainfall than normal throughout the month. The agency is also saying that there is a possibility of cyclone formation in the Bay of Bengal this month. In its long-term weather forecast for October, the Meteorological Office said that two to three low-pressure areas may form this month, one of which may develop into a depression or cyclone. The forecast also says that the southwest monsoon may depart from Bangladesh by the first half of October. And in the second half, day and night temperatures may gradually decrease. In addition, there is a possibility of thunderstorms in the country for three to four days this month. Also, the southwest monsoon may depart from Bangladesh by the first half of the month. After that, the rainfall trend may decrease and the temperature may also gradually decrease towards the end of the month, meteorologists said. But why is it raining in early October? How long can this rain continue? And why is the possibility of a cyclone being talked about even though the rainfall is forecast to decrease?
Why is it raining, how long will it last?
In the context of Bangladesh, October is the end of the monsoon season and the beginning of the dry season. During this time, the monsoon winds gradually began to depart from Bangladesh and the influence of the westerly winds associated with winter weather began to increase. In other words, the monsoon is active over Bangladesh, said meteorologist Md. Toriful Newaz Kabir. He told BBC Bangla that usually the monsoon starts to depart from Bangladesh in the first 10 days of October. However, this time the monsoon is still in flow. Recently, a distinct low pressure area near Myanmar and southeastern Bangladesh later developed into a depression, disrupting the normal flow of monsoon winds to some extent. Even though the low pressure has been deactivated, the monsoon flow has not completely stopped. On the other hand, the westerly wind is also slowly moving towards Bangladesh.
"When the monsoon winds leave, the western winds will come and after that the temperature will gradually decrease... In other words, both of these are now trying to take over. And because of this, although the monsoon winds are now flowing, it is relatively weak. With it, water vapor is coming sporadically. Due to this, clouds are forming in different places and it is raining," said Mr. Kabir. According to him, such conditions may persist for another four to five days, and during this period, the rainfall trend will be relatively high in the eastern part of the country. In particular, there is a possibility of rain or thundershowers in various places of Khulna, Barisal, Chittagong, Sylhet, Dhaka and Mymensingh divisions in the next 24 hours. Rangpur and Rajshahi may remain relatively dry during this time. However, the tendency of rain may increase in Rangpur and Rajshahi for one or two days later.
After that, the rainfall trend across the country will decrease significantly.
"The rain will decrease from October 10th onwards. Then the temperature may increase slightly. Because even though the rain has decreased, the sun has not yet moved too far south. However, the temperature will start to gradually decrease towards the end of October," added the meteorologist. According to him, the temperature at the beginning of winter this year may be slightly higher than other years. "This year, due to El Nino, there will be a warm winter worldwide, meaning temperatures will not be low. Just like in other years, we see temperatures drop immediately after the rain, this time it will take a little longer." The Meteorological Department's month-long forecast says that two to three low-pressure areas may form in the Bay of Bengal in October. One of these may develop into a depression or cyclone.
However, it is not possible to say specifically where a potential cyclone will form, what its trajectory will be, or whether it will have an impact on Bangladesh. Basically, there is a tendency for cyclones to form in the Bay of Bengal, usually before the arrival of the monsoon in Bangladesh and after the departure of the monsoon. Meteorologist Tariful Newaz Kabir says that since it is time for the monsoon to depart, it is also a normal time for cyclones to form in the Bay of Bengal. "The monsoon leaves in October, so naturally it is the time for cyclones. In previous years, Bangladesh has also had major cyclones in October-November," he said. In other words, there is no inconsistency between the possibility of cyclones occurring with the decrease in rainfall in October. Rather, the Bay of Bengal tends to form cyclones during this period of the monsoon's retreat. However, Mr. Kabir says that the pattern of monsoon rains this time was slightly different compared to the last few years.

According to him, in the last three-four years, there was relatively less rain in the beginning of the monsoon season, but the amount of rain increased in September-October. But this time there was a lot of rain in June-July-August, there was some in September too, and since then the trend of rain has started to decrease. "This time, the situation is exceptional compared to the last three-four years. June to August are the rainy months in Bangladesh. But for a few years, there was no rain at all during this period, and it finally did. This time, nature has followed its rules. I think it is positive," he said. However, the meteorologist also noted that the amount of rainfall has decreased slightly this year towards the end due to the influence of El Niño.
How much rain has there been in October in recent years?
It is clear that it is not unusual for rain to occur in Bangladesh in October. The Meteorological Department's data from previous years also shows significant rainfall in various parts of the country, including Dhaka, in October. Bangladesh usually receives an average of 10,447 millimeters of rainfall in October. However, in October last year, a total of 8,736 millimeters of rainfall was recorded across the country, which was 30.5 percent less than normal rainfall. And that month, Dhaka Division alone received 1,518 millimeters of rainfall. Previously, in 2024, 2,626 millimeters of rainfall was recorded in Dhaka Division and 19,111 millimeters across the country.
In 2023, 2,196 millimeters of rainfall occurred in Dhaka Division and 11,237 millimeters across the country. The previous year, during the same period in 2022, a total of 1,872 millimeters of rainfall was recorded in Dhaka Division and 9,783 millimeters across the country. And, in October 2021, a total of 869 millimeters of rainfall occurred in Dhaka Division and 8,642 millimeters across the country. In October 2020, the year of the Corona pandemic, 921 millimeters of rainfall was recorded in Dhaka Division and 9,764 millimeters across the country. And while a total of 35 millimeters of rain was recorded across the country on October 1st of this year, a total of 36 millimeters of rain was recorded across the country between 6 am and 12 noon today, October 2nd, of which 21 millimeters fell in Nikli. Meteorologist Kazi Jebunnesa said that there may have been rain in some other places besides this. However, since there are no observation centers in all places, they do not have information on rainfall in those areas. Earlier, meteorologist Bazlur Rashid told BBC Bangla that the monsoon winds depart in the first or second week of October. As a result, it rains during this time.