Bangladesh could experience between four and six mild to moderate cold waves from November to January, with two to three potentially intensifying into severe cold spells, according to the Bangladesh Meteorological Department (BMD). Despite the possibility of several cold waves, the overall winter season is expected to be relatively warmer than usual, with average daytime and night-time temperatures likely to remain above normal under the influence of El Niño.

The forecast is part of the BMD’s three-month long-range weather outlook covering November, December and January. It also highlights the possibility of dense fog, seasonal rainfall, low-pressure systems over the Bay of Bengal and the potential development of tropical cyclones.

Explaining the likely timing and geographical distribution of the cold spells, meteorologist Dr Muhammad Abul Kalam Mallick told the Bangladesh Sangbad Sangstha (BSS) that one or two mild cold waves could affect the country in December.

The northern and western regions are expected to experience the greatest impact. Parts of Rajshahi, Rangpur and Khulna divisions could see temperatures fall to between 8 and 10 degrees Celsius during these episodes.

January may bring more intense conditions. According to Dr Mallick, moderate cold waves are possible during the month, alongside one or two severe cold spells. Temperatures in some areas could drop to between 4 and 6 degrees Celsius.

Dense fog could intensify the feeling of winter

Moderate to dense fog is likely in different parts of the country, particularly over river basins, from late night until the morning throughout the three-month period. Other areas may experience light to moderate fog.

Dense fog can restrict daytime sunshine and limit the rise in temperature, reducing the difference between daytime and night-time readings. As a result, people may feel colder even when recorded temperatures remain relatively close to the seasonal average.

However, the overall temperature outlook suggests that both daytime and night-time averages could remain above normal.

Dr Mallick attributed this tendency to the influence of El Niño and global warming, which could contribute to higher average temperatures across Bangladesh and other parts of South Asia.

He said that, although the season was expected to be comparatively warm, temperatures could still fall below 10 degrees Celsius at times, triggering cold waves. The number, duration and geographical spread of extremely severe cold spells, however, are expected to remain relatively limited.

The meteorologist also cautioned that uncertainty remains over the frequency and duration of cold waves because of the influence of El Niño. The seasonal outlook should therefore be treated as a broad indication rather than a precise prediction of conditions on individual days.

Bay of Bengal may see up to four low-pressure systems

Alongside the winter forecast, the BMD has predicted that between two and four low-pressure systems could develop over the Bay of Bengal during the next three months. One or two of these systems may strengthen into cyclones.

Dr Mallick noted that October and November are generally considered cyclone-prone months in the region. Low-pressure systems frequently develop over the Bay of Bengal during this period, and some may gain strength under favourable atmospheric and oceanic conditions before developing into cyclonic storms.

He also explained that the seasonal movement of the Sun towards the Southern Hemisphere reduces daylight hours and increases the length of nights. However, the availability of solar radiation over parts of the Bay of Bengal can contribute to higher sea-surface temperatures. This is part of the natural seasonal process, although the same atmospheric and oceanic conditions do not necessarily develop every year.

Rainfall expected to remain within normal limits

The BMD expects overall rainfall across Bangladesh to remain within the normal range during the November-January period. However, the amount of rainfall is likely to vary between divisions and months.

Chattogram Division is forecast to receive the highest rainfall in November, with an estimated 35-40 millimetres. Barishal may receive 30-40 millimetres, while Dhaka, Sylhet and Khulna could record between 15 and 25 millimetres.

Mymensingh and Rajshahi divisions are expected to receive 10-15 millimetres, while Rangpur may see comparatively little rainfall, at around 4-8 millimetres.

Rainfall is likely to decrease further in December and January. In December, Dhaka Division is expected to receive 8-10 millimetres, while Sylhet may record 10-15 millimetres.

In January, Khulna Division could receive 10-14 millimetres of rain. Other divisions, including Dhaka, are forecast to receive between 6 and 10 millimetres.

These figures represent the department’s regional projections for the three-month period and may vary as weather systems develop.

Historical data and climate models underpin the forecast

The BMD said the long-range outlook was prepared by analysing a range of meteorological information, including upper-air atmospheric patterns, climate models and forecasts from international centres authorised by the World Meteorological Organisation (WMO). Both El Niño and La Niña conditions were also considered during the assessment.

Explaining the historical basis of the forecast, Dr Mallick said the department had examined records of low-pressure systems that developed over the Bay of Bengal during October and November between 1948 and 2025.

The analysis showed that an average of one to three low-pressure systems develop over the bay during these months. Some of them may strengthen and eventually develop into cyclones, depending on prevailing atmospheric and oceanic conditions.

He stressed that long-range forecasts are subject to a relatively high degree of uncertainty. Such projections are based on historical patterns, climate indicators and model simulations, rather than the precise prediction of daily weather conditions several months in advance.

For that reason, he advised the public to follow regular daily weather bulletins alongside the seasonal outlook, particularly when cold waves, dense fog or potential cyclonic systems are forecast.

How cold waves are classified in Bangladesh

According to the BMD, cold waves are classified into four categories based on the minimum recorded temperature:

• Mild cold wave: 8-10 degrees Celsius.
• Moderate cold wave: 6-8 degrees Celsius.
• Severe cold wave: 4-6 degrees Celsius.
• Very severe cold wave: Below 4 degrees Celsius.

The classifications help distinguish between different levels of cold-weather intensity and provide a basis for assessing the potential impact of falling temperatures.

Overall, Bangladesh is likely to face several cold spells during the coming winter, particularly in its northern and western regions. Although the broader seasonal outlook points towards warmer-than-normal conditions, periods of sharp temperature declines and dense fog remain possible. Residents, especially those in areas prone to cold waves, will need to remain attentive to updated weather forecasts as the season progresses.