The familiar rhythm of winter is changing: late cold, more smog and new risks for crops
Dew-soaked grass, fog-covered paths, a chilly morning breeze and date-palm tappers busy collecting juice — at one time nature announced the arrival of winter right at the start of Agrahayan. As the cold deepened in Poush and Magh, sunbathing in courtyards, the smell of steamed rice cakes and mornings wrapped in thick fog became the familiar face of a Bengal winter.
But that familiar scene is changing with time. Often the feeling of heat does not fade even after Agrahayan passes, and fans or air conditioners still run in places during the day. And when winter does bite, it comes late — sometimes at the end of Poush, sometimes in mid-Magh.
Winter in Bangladesh is generally considered to run from December to February, when temperatures fall and humidity and fog patterns change. In recent years, however, the season's arrival, duration and intensity have grown irregular. Some years winter comes late; some years it turns intense briefly and then eases; elsewhere a few days of cold wave are followed by rising temperatures.
Climate change is a key backdrop to this shift. A 2024 Bangladesh climate factsheet published by the Research Centre for Climate Change (RCCC) says the country's average annual temperature rose by about 0.1 to 0.2 degrees Celsius per decade between 1961 and 2015 — a long-term observation pointing to a warming trend.
The Bangladesh Meteorological Department's report 'Changing Climate of Bangladesh' also analysed temperature changes at weather stations across the country from 1980 to 2020. Separately, a study on Dhaka found winter average minimum temperatures rising by about 0.45 degrees Celsius per decade over 1980–2020 — a Dhaka-specific figure that cannot be taken as the picture for the whole country.
Expert observation and these studies suggest long-term climate change is affecting winter's familiar character. Yet a late or mild winter in any single year also depends on wind flow, cloud cover, fog and regional weather conditions, so one or two winters' experience cannot explain the full picture of climate change.
Winter mornings once meant nature wrapped in thick fog. In many cities and industrial areas, that picture has changed: pollution-driven smog now mixes with natural fog, and the two are often hard to tell apart.
In winter, low wind speed, scant rainfall and a stable atmosphere prevent polluted particles from dispersing easily. Vehicle exhaust, brick-kiln emissions, construction dust and industrial pollution make the situation worse, so in many areas people breathe polluted air instead of winter's clean air.
The Department of Environment's report 'Ambient Air Quality in Bangladesh' documents winter air pollution: compared with summer, PM2.5 concentrations in winter were 28 percent higher in Agargaon and 77.6 percent higher in Narayanganj, while Savar saw an increase of around 63 percent. Winter, in other words, is not only the season of falling temperatures; in many areas the risk of air pollution rises too.
Polluted air hits children, elderly people and those with respiratory problems hardest. Ensuring clean air has therefore become a major environmental challenge alongside enjoying winter's beauty.
Bangladesh's agriculture is closely tied to the weather. The natural growth of many crops depends on winter temperature, fog, dew and sunlight. Abnormal temperature swings, irregular winters or prolonged fog can affect crop growth and production.
Winter vegetables, potatoes, mustard and other crops need specific weather conditions. Higher temperatures can disrupt the normal growth of some crops, while excessive fog and humidity raise the risk of disease in others — forcing farmers to change their production plans and cultivation strategies.
The impact is not limited to agriculture; biodiversity is affected too. The life cycles of plants and animals adapted to winter can shift with temperature and season changes, and weather also plays an important role in the arrival, movement and feeding of migratory birds.
Climate change is not the only reason winter's atmosphere is fading. Urbanisation, changing lifestyles and people's growing distance from nature are also causes. Still, when the natural rhythm of the seasons changes, it affects livelihoods and cultural habits as well.
Responding to this situation requires cutting greenhouse gas emissions globally alongside effective action at national and local levels. Stopping indiscriminate tree felling, planting trees and protecting forests, saving water bodies, controlling air pollution and expanding environment-friendly fuel use are all essential — as are effective steps to control vehicle and industrial emissions and reduce construction dust.
