Bangladesh Weather 2026: What You Need to Know Before the Season Begins

Bangladesh experiences four overlapping natural hazard seasons annually: the pre-monsoon period (March–May) with nor'westers and cyclone risk, the monsoon flood season (June–September), the post-monsoon cyclone window (October–November), and the winter dry period (December–February). April 2026 sits at the beginning of the most dangerous 90-day stretch of the Bangladesh weather calendar — the pre-monsoon window when cyclones form in the Bay of Bengal, Kalbaishakhi storms hit inland districts without warning, and haor region flash floods begin before the official monsoon even arrives. This guide covers the monsoon calendar, cyclone history and risk zones, the most flood-prone districts, how to read Bangladesh Meteorological Department alerts, emergency contacts, and practical preparation steps.

When Does Monsoon Season Start in Bangladesh 2026?

The Bangladesh monsoon follows a predictable but not perfectly consistent geographic progression. In a typical year, the pattern is as follows. The monsoon onset at Cox's Bazar and the southeastern coast of Bangladesh occurs between late May and early June — usually around May 25–June 5. It reaches Chittagong between June 1–10, Dhaka and central Bangladesh between June 10–20, and Sylhet and the northeastern haor region — which often receives the earliest and heaviest rain due to overflow from India's Meghalaya and Assam — sometimes as early as late May. The monsoon covers all of Bangladesh by late June to early July in most years. It typically begins to withdraw from the northwest in early October and retreats fully from the southeast by late October.

The 2024 monsoon was among the most damaging in recent years. The season began with Cyclone Remal on May 26, 2024, followed by a series of haor flash floods in June and major Jamuna basin flooding in July–August. The UN estimated 18 million people were affected across the full 2024 flood season. The 2025 monsoon began in mid-May with heavy rainfall and a Bay of Bengal depression making landfall on May 29, affecting Sylhet, Sunamganj, Moulvibazar, Habiganj, Netrokona, Noakhali, Bhola, Khagrachari, Bandarban, and Rangamati. BMD does not pre-publish an official monsoon onset date — forecasts are issued progressively as the season approaches.

Critically, the pre-monsoon period beginning in April is not a safe interlude before the flood season. It is the primary cyclone formation window and the season of Kalbaishakhi (nor'westers) — the fast-moving storm cells that strike Dhaka and central Bangladesh in the afternoon and evening, typically March through May, bringing sudden heavy rain, hail, lightning, and wind gusts up to 80–100 km/h with minimal warning time. These storms cause significant damage to makeshift housing, electrical infrastructure, and road trees every year.

Bangladesh Cyclone Season 2026 — Dates, History and Risk Zones

Bangladesh has two cyclone formation windows annually, both originating in the Bay of Bengal. The pre-monsoon window runs from April through June, with May historically being the most active month. The post-monsoon window runs from October through December, with October and November historically producing the most intense storms. The Bay of Bengal is one of the world's most cyclone-active water bodies, and Bangladesh's geography — a low-lying delta at the head of the Bay — makes it uniquely exposed to both direct landfall and storm surge amplification.

Bangladesh's modern cyclone disaster history shows a dramatic reduction in deaths over time — from 147,000 in the 1991 Cyclone Gorky to 3,447 in Cyclone Sidr (2007) to 16 in Cyclone Remal (2024). This improvement is attributed primarily to the Cyclone Preparedness Programme (CPP), established in 1973 as a joint initiative of the Government of Bangladesh and the Bangladesh Red Crescent Society. The CPP operates a network of over 76,000 trained volunteers across the 13 coastal districts. When BMD issues a warning, CPP volunteers deploy within hours to begin evacuation of the most vulnerable communities.

The 13 sea-facing coastal districts that form Bangladesh's primary cyclone risk zone are: Cox's Bazar, Chittagong, Noakhali, Lakshmipur, Feni, Chandpur, Bhola, Barisal, Pirojpur, Jhalokathi, Barguna, Patuakhali, and Satkhira. Of these, Cox's Bazar, Chittagong, Bhola, Patuakhali, and Barguna have historically experienced the most frequent direct landfalls. The Sundarbans mangrove forest in the southwest provides partial natural protection for Khulna and Bagerhat, absorbing wind and surge energy — though as Cyclone Sidr (2007) demonstrated, this protection is partial rather than complete.

Storm surge — not wind — is the primary killer in Bangladesh cyclones. The 1970 Bhola Cyclone killed an estimated 300,000–500,000 people primarily through surge flooding of the delta islands. Cyclone Sidr's 5–6 meter surge inundated vast areas of the southwest coast within hours of landfall. Cyclone Remal (2024) produced a 5–8 foot surge in coastal districts of Khulna, Bagerhat, Satkhira, Patuakhali, and Barguna, affecting 4.6 million people across 19 districts. The key practical implication: when Signal 7 or above is issued for your district, evacuate immediately — do not wait for Signal 10. By the time Signal 10 is issued, roads in low-lying coastal areas may already be flooding.

Bangladesh Cyclone Signal System — What Each Level Means

The Bangladesh Meteorological Department uses a numbered signal system for both river ports (inland) and sea ports (coastal). The levels that require action are as follows. Signal 1 means a distant storm has formed — awareness only. Signal 3 indicates a storm is a potential threat — begin preparations, monitor BMD bulletins. Signal 4 means a storm is a moderate threat — prepare for evacuation if in a coastal district. Signal 7 means the storm is a serious threat and may make landfall — evacuate if you are in a coastal or low-lying area. Signal 10 is the highest level — the storm is imminent and extreme danger is present. Evacuation should already be complete before Signal 10 is issued.

BMD issues Special Weather Bulletins during active cyclone events, updated every three hours as storm approach accelerates. These are available on the BMD website (bmd.gov.bd), Bangladesh Television, Bangladesh Betar radio, and through the 333 national helpline. A battery-powered or hand-crank radio is the most reliable information source during cyclone landfall, as mobile networks and electricity often fail simultaneously.

Flood-Prone Districts — Sylhet, Sunamganj, Netrokona, Kurigram and More

Bangladesh's flood geography follows its river systems and haor basins. Understanding which type of flooding affects which area is essential for practical preparation. The country experiences four distinct flood categories.

Haor region flash floods (northeast) affect Sylhet, Sunamganj, Moulvibazar, Habiganj, Netrokona, and Kishoreganj. These floods are caused by extreme rainfall over the Meghalaya Plateau in India, which drains rapidly into Bangladesh's haor (wetland) basins. They can inundate an entire haor within 24–48 hours, often before the official monsoon onset — the earliest haor floods typically occur in late April or May. The 2024 haor floods began in June shortly after Cyclone Remal and by mid-June had put 75% of Sylhet district under water.

Jamuna basin floods (north-central) affect Kurigram, Gaibandha, Jamalpur, Sirajganj, Tangail, and parts of Bogura. These are driven by snowmelt and monsoon rainfall in India and Nepal flowing down the Brahmaputra-Jamuna system. Peak flooding typically occurs July–August. Kurigram and Gaibandha are the most consistently inundated districts — char (riverine island) communities in these districts face annual displacement.

Ganges-Padma corridor floods (central-west) affect Rajshahi, Faridpur, Rajbari, Manikganj, and Munshiganj, typically August–September. The catastrophic 1998 flood — which covered two-thirds of Bangladesh for 65 days — was caused by the simultaneous peaking of the Jamuna, Ganges, and Meghna systems within the same two-week window.

Southeastern flash floods and coastal flooding affect Feni, Noakhali, Cumilla, Chittagong, Rangamati, Khagrachari, and Bandarban. These districts receive flash flooding from the Chittagong Hill Tracts and are simultaneously exposed to cyclone-driven coastal flooding. The August 2024 floods that cut off over one million people were concentrated in Feni and adjacent districts, with Feni experiencing near-total inundation.

Urban flooding in Dhaka has been worsening as natural water retention areas (khals, wetlands, and low-lying land) are converted to construction. Dhaka waterlogging after heavy Kalbaishakhi storms or monsoon rainfall is a recurring annual phenomenon in low-lying areas including Mirpur, Mohammadpur, Demra, Jatrabari, and Rayer Bazar.

How to Prepare for Cyclones and Floods — Practical Checklist

The Bangladesh Meteorological Department and the Cyclone Preparedness Programme recommend completing household preparedness before the peak pre-monsoon window opens in late April. The CPP distributes preparation checklists through its 76,000+ volunteer network in coastal districts. The following applies to both cyclone and flood preparation.

Emergency supplies: Store a minimum three-day supply of dry food in sealed waterproof containers — rice, lentils, dried fish, biscuits, and oral rehydration salts (ORS). Store at least 10 litres of clean drinking water per household member in sealed containers. A battery-powered or hand-crank radio is essential — mobile networks and electricity fail during cyclone landfall. Keep waterproof document pouches containing your National ID card, land documents, and bank records. After a cyclone, these documents determine access to government relief and rebuilding assistance.

Before a cyclone warning: Know the location of your nearest cyclone shelter. Know the evacuation route from your home to that shelter. When Signal 7 is issued for your district, begin moving to the shelter — do not wait for Signal 10. Register at the shelter — unregistered households may not receive relief assistance. Secure or move livestock if time permits.

During the cyclone: Stay inside the shelter until authorities confirm it is safe to leave. Do not go outside during the eye of the storm — the calm period is temporary and the back wall of the storm will arrive within 30–90 minutes. Keep children together and account for all household members.

After a cyclone: Do not use well water or surface water without testing or treatment — storm surge contaminates fresh water sources with saline water. Seek medical attention for any wounds immediately — wound infections in flood conditions progress rapidly. Report to your local Union Parishad (UP) or upazila disaster management committee for relief registration.

For flood preparation in haor and river basin districts: Identify the nearest elevated ground or embankment. Keep a small emergency boat or inflatable tube accessible if your homestead is adjacent to a river or haor. Monitor FFWC (Flood Forecasting and Warning Centre) alerts at ffwc.gov.bd for river level data updated every three to six hours during the flood season.

How to Read Bangladesh Meteorological Department Weather Alerts

The Bangladesh Meteorological Department (BMD) is the primary authoritative source for all weather warnings in Bangladesh. Its main portal is bmd.gov.bd. Key features of the BMD website include: current weather conditions for all major stations, 48-hour and 72-hour forecast maps, radar imagery (updated every 30 minutes during active weather), satellite imagery, and the Special Weather Bulletin archive during cyclone events.

During monsoon season, BMD issues a daily weather bulletin covering rainfall forecasts for all divisions. During cyclone events, Special Weather Bulletins are issued and updated every three hours with the storm's position, intensity, projected path, and signal level for each coastal district. The BMD also operates a weather data portal at bmddataportal.com for historical rainfall and station data.

The Flood Forecasting and Warning Centre (FFWC), under the Bangladesh Water Development Board, provides real-time river level monitoring at over 100 river stations nationwide. Its portal at ffwc.gov.bd shows current water levels compared to danger levels for each station, with trend arrows indicating whether levels are rising, steady, or falling. During June–September, FFWC publishes 24-hour and 72-hour flood forecasts for major river systems.

Emergency Contacts — Disaster Management, BDRCS and Fire Service

ServiceContactWhen to Use National Emergency Helpline999Police, Fire, Ambulance — all emergencies National Service Helpline333Government information, disaster alerts, service access Fire Service & Civil Defence16163Fire emergencies, search and rescue Bangladesh Red Crescent (BDRCS)bdrcs.org / 02-9330188Disaster relief, blood services, CPP volunteer coordination Dept. of Disaster Management (DDM)modmr.gov.bdOfficial government disaster response; relief registration Bangladesh Meteorological Dept.bmd.gov.bdCyclone signals, weather bulletins, rainfall data Flood Forecasting & Warning Centreffwc.gov.bdReal-time river levels, flood forecasts CPP Cyclone Preparedness ProgrammeVia BDRCS / local UPCoastal cyclone evacuation coordination Dhaka WASA Waterlogging16162Urban flooding, drainage complaints in Dhaka Coast Guard01769-800800Maritime emergencies, river/coastal rescue

Bangladesh Weather Seasonal Calendar 2026

PeriodSeasonPrimary HazardsMost Affected Districts March–MayPre-MonsoonNor'westers (Kalbaishakhi), cyclone formation, early haor floodsAll districts (storms); northeastern haor region; coastal districts (cyclone) Late May–JuneMonsoon OnsetCyclone landfall (May–June peak), haor flash floods, early river floodingSylhet, Sunamganj, Netrokona; coastal districts July–AugustPeak MonsoonJamuna basin flooding, monsoon river floods, landslides (CHT)Kurigram, Gaibandha, Sirajganj; Rangamati, Bandarban, Khagrachari August–SeptemberLate MonsoonGanges-Padma floods, southeastern flash floodsRajshahi, Faridpur; Feni, Noakhali, Cumilla October–NovemberPost-MonsoonCyclone (second peak), storm surge, residual floodingAll 13 coastal districts; Chittagong Hill Tracts December–FebruaryWinterCold wave, fog (transport disruption), river erosionNorthern districts (Rangpur, Rajshahi divisions)

Weather, Disaster and Bangladesh's Economic Resilience

Bangladesh's weather and disaster calendar is not separate from its economic story — it is embedded in it. The 2024 flood season affecting 18 million people across multiple events compressed into a single season produced agricultural losses, infrastructure damage, and displacement that shaped the economic data for FY2025. The August 2024 floods in Feni and the southeast coincided with the political transition of the same period, compounding the challenge for relief coordination. For the Bangladesh economic outlook and how weather-related shocks factor into growth projections, see our Bangladesh GDP forecast 2026 analysis.

The West Asia war that began February 28, 2026 introduces an energy dimension to Bangladesh's disaster preparedness. Bangladesh relies on diesel generators extensively during power outages — which cyclones cause at scale. Cyclone Remal (2024) left 20 million people without electricity; restoring power required diesel for generators throughout the restoration period. At $110–120/barrel Brent crude in early 2026, the cost of emergency diesel supply for post-cyclone power restoration is substantially higher than it was in previous years. For analysis of how the West Asia conflict is affecting Bangladesh's energy and economic position, see our global oil crisis and energy prices impact on Bangladesh.

Bangladesh's disaster management system is internationally recognised as one of the most effective in the developing world. Death tolls from cyclones have fallen from hundreds of thousands to tens in five decades. The CPP volunteer network, the 4,000+ coastal cyclone shelters, the BMD early warning system, and the FFWC flood forecasting network represent a genuine infrastructure of survival. Using it — monitoring alerts, knowing your shelter, evacuating when signals indicate — is the most important weather safety action any Bangladeshi household can take.

Frequently Asked Questions

When does monsoon season start in Bangladesh 2026?
The monsoon typically reaches Cox's Bazar and the southeastern coast of Bangladesh between late May and early June, arriving in Dhaka and central Bangladesh around June 10–20, and covering the entire country by late June to early July. The pre-monsoon period from April onward brings nor'westers, early haor flash floods, and cyclone risk before the official monsoon onset.

When is Bangladesh cyclone season 2026?
Bangladesh has two cyclone windows: pre-monsoon (April–June, with May the most active month) and post-monsoon (October–December, with October–November the most active). Both form in the Bay of Bengal. The 13 sea-facing coastal districts are the primary risk zone.

Which Bangladesh districts are most flood-prone?
The highest-risk districts by flood type: haor flash floods — Sylhet, Sunamganj, Netrokona, Moulvibazar; Jamuna basin flooding — Kurigram, Gaibandha, Sirajganj, Jamalpur; southeastern flash floods — Feni, Noakhali, Cumilla, Chittagong; coastal surge flooding — all 13 sea-facing coastal districts.

What is the BMD cyclone signal system in Bangladesh?
BMD uses numbered signals from 1 to 10. Signals 1–3 indicate awareness and preparation stages. Signal 7 means a serious threat — coastal residents should begin evacuation. Signal 10 is the maximum — evacuation should be complete before this level is reached, as roads in low-lying areas may already be flooding.

What are the emergency contacts for disasters in Bangladesh?
National emergency: 999. National helpline (government services, disaster information): 333. Fire Service: 16163. Bangladesh Red Crescent (BDRCS): 02-9330188. BMD weather alerts: bmd.gov.bd. Flood forecasts: ffwc.gov.bd. Coast Guard: 01769-800800.