First monsoon in 25 years arrives early due to La Niña

In the Bengali calendar, the months of Asharh and Shraban mark the monsoon season. This season begins with the entry of the southwest monsoon winds into Bangladesh. However, due to the active presence of La Niña, the southwest monsoon is set to arrive earlier than usual this year. By the first week of June, the monsoon is expected to spread across the country—a phenomenon that hasn’t occurred in the past 25 years. The last instance of early monsoon in Bangladesh was in the year 2000.

Meteorologist A.K.M. Nazmul Haque told Views Bangladesh that the Pacific Ocean region has experienced the presence of La Niña over the past few years. La Niña is the opposite of El Niño. When La Niña is active, the prevailing wind patterns across the Pacific Ocean shift from east to west, driving warm water westward. This causes cold water from the depths to rise to the surface in the eastern Pacific, significantly lowering sea surface temperatures there. While El Niño is associated with extreme heatwaves, La Niña typically brings cooler weather and affects rainfall patterns, often causing early and increased monsoon rainfall. This year, La Niña is particularly active, resulting in noticeable changes in regional weather patterns. In fact, the Indian subcontinent has not witnessed such Pacific Ocean conditions during the monsoon season in the past 25 years. As a result, early monsoon is expected not only in Bangladesh but also across India, Myanmar, Thailand, Malaysia, Indonesia, Laos, and Vietnam.

Mustafa Kamal Palash, a weather and climate researcher at the University of Saskatchewan in Canada, stated in a verified Facebook post on May 27 that, based on the latest forecasts from European Union and U.S. weather models, the southwest monsoon is expected to reach the Teknaf coast of Bangladesh on Saturday, May 31 (17 Jyaishtha). The timeline for monsoon expansion across the country is as follows:

June 1: Cox’s Bazar

June 2: Chattogram

June 3: Barishal, Khulna, Cumilla

June 5: Dhaka, Sylhet, Mymensingh

June 6: Rajshahi

June 7: Rangpur


During this period, relatively higher rainfall is expected in the following districts: Chattogram, Cox's Bazar, Feni, Jashore, Satkhira, Khulna, Jhenaidah, Faridpur, Madaripur, Gopalganj, Magura, Rajbari, Manikganj, Munshiganj, Barguna, Barishal, Pabna, Sirajganj, Jamalpur, Tangail, Mymensingh, Netrokona, Sunamganj, and Sylhet. In addition, the southwest monsoon is expected to enter the coastlines of Odisha and West Bengal in India on May 30 via the northwestern Bay of Bengal.

Meteorologist Khandakar Hafizur Rahman told Views Bangladesh that the monsoon generally follows a fixed seasonal pattern. However, climate change is disrupting these regular rhythms. Global warming, changes in sea surface temperatures, and various atmospheric anomalies are all contributing to this disruption. Rising global temperatures are altering atmospheric pressure and wind flow directions. Due to above-normal sea surface temperatures in the Bay of Bengal, the monsoon winds have rapidly intensified. At the same time, the effects of La Niña in the Pacific Ocean are accelerating the early onset of the monsoon in Bangladesh. “This year, rainfall may also be somewhat heavier than usual,” he added.

When asked about the potential impacts of early monsoon, he said, “For farmers, especially those cultivating Boro rice, early rains can offer some relief—if they manage to harvest their crops on time, they might avoid losses. On the other hand, excessive or untimely rainfall could severely damage crops. Early monsoon can lead to rising river levels, increasing the risk of sudden floods. Heavy rain in the hilly regions could also trigger landslides, and the risk of cyclones may rise as well.”

However, he emphasized that early arrival of the monsoon does not necessarily mean it will end early. In fact, the monsoon season may be prolonged this year, raising the possibility of extended flooding. Ultimately, the impact will depend on the volume of rainfall. If there is no extreme or abnormal rainfall, this early monsoon could be considered beneficial for nature.