Back to mildness after 2 decades between El Niño and La Niña

Bangladesh, known for its six seasons, has traditionally been classified as having a temperate climate—one that lies between the extremes of the tropical and polar zones. The hallmark of this climate is moderate temperatures, with neither severe cold nor intense heat, and regular rainfall. However, for more than two decades, this temperate sensation had all but vanished from Bangladesh. In its place, the country experienced increasingly extreme weather conditions, with harsher winters, scorching summers, and irregular monsoons. Other seasons came and went with little distinction. During summer, parts of the country, especially Rajshahi, would often be swept by hot, desert-like "loo" winds. But this year marks a return of temperate weather to Bangladesh after nearly 20 years, with moderate summer temperatures and rainfall. Climate experts predict a normal monsoon and no severe winter chill ahead.

Naturally, the question arises: why has the weather returned to normalcy after such a long hiatus?

According to meteorologists and climate experts, the weather patterns across Bangladesh and the greater Indian subcontinent are heavily influenced by the state of the Pacific Ocean. Over the past few years, the region has been under the influence of "La Niña," which is the opposite of "El Niño." During a La Niña phase, wind patterns shift across the Pacific Ocean from east to west, drawing cold water from deep within the ocean to the surface, causing sea surface temperatures in the eastern Pacific to cool significantly. While El Niño is linked to extreme heatwaves, La Niña typically has the reverse effect. However, it too disrupts rainfall patterns, often leading to excessive rainfall and other anomalies.

This time, however, nature appears to be taking a different turn. The latest La Niña phase ended in December, which explains the absence of a harsh winter this year. El Niño is still months away—it will take another nine months or so to form. In the meantime, the Pacific Ocean remains in a "neutral" state, and this neutrality is allowing for stable, temperate weather in Bangladesh. This year, unlike the last when the country endured heatwaves every day of April, no such extreme has been observed. And with El Niño still at least five months away, the upcoming monsoon is expected to bring normal rainfall. Likewise, there is little risk of prolonged cold spells in the winter ahead.

Meteorologist Bazlur Rashid explained that it typically takes around eight to nine months for the Pacific to transition from one state (La Niña or El Niño) to the other. During this period, the ocean enters a "neutral" phase. The water gradually moves from cold to warm temperatures, and this transition takes time. Similar neutral phases have been recorded in the past. He noted, "The monsoon season this year falls within this neutral window. In the past 25 years, the Indian subcontinent has not experienced such a neutral phase during monsoon. It has always been under either La Niña or El Niño conditions. This year is an exception. Thanks to this neutrality, India is also expected to have normal rainfall during the monsoon."

He added that while rainfall may return to normal, other weather indicators remain uncertain. However, with the ocean in a neutral phase, extreme events such as storms, unusual wind flows, and severe temperature shifts are unlikely.

Meteorologist Khandaker Hafizur Rahman stated, “After more than two decades, Bangladesh is experiencing a neutral phase between La Niña and El Niño. While not unheard of, it is certainly rare. Before climate change began to amplify the effects of El Niño and La Niña, such neutral phases were more common—and Bangladesh’s climate was typically mild. That’s why the country used to be considered a temperate region. After many years, that temperateness is back. This year, April—the hottest month—has been relatively mild. The coming monsoon is expected to bring normal rainfall, and the next winter is unlikely to bring prolonged cold spells.”

When asked why this shift occurred, he said, “No one controls nature. We can only say that this is a welcome relief.”

Meanwhile, former climate scientist Parthasarathi Mukhopadhyay of the Indian Institute of Tropical Meteorology in Pune told the BBC that every time the Pacific transitions from a La Niña to an El Niño phase (or vice versa), there is a 9–10 month neutral period in between. That is what we are experiencing now. It takes time for ocean temperatures to shift from cold to normal and then from normal to warm. “There’s nothing novel in that,” he said. “This year, both summer and monsoon seasons coincide with this neutral phase. In the past 25 years, the Indian subcontinent has not experienced such a neutral phase during this time—it has always been under the influence of either La Niña or El Niño. This time is different. But if we want to enjoy this kind of soothing exception more often, we must overcome every obstacle to protecting our environment.”