Bangladesh Cyclone Season 2026: Warning Signals, Preparation Checklist, and What the Early Warning System Actually Does

A Country Built in the Path of Storms

Bangladesh sits at the northern apex of the Bay of Bengal — a triangular body of water that functions, in meteorological terms, as a cyclone accelerator. Warm sea surface temperatures, shallow coastal bathymetry, and the funnel geometry of the bay combine to amplify tropical cyclones as they move north toward the delta. The Ganges-Brahmaputra-Meghna delta, where most of Bangladesh sits, is one of the lowest-elevation populated landmasses on earth. More than 700 rivers thread through it. Much of the coastal zone is less than three meters above sea level.

The consequence is a death toll across two centuries that has no parallel for any other single country. A total of 775,303 people died in coastal and offshore areas of Bangladesh from cyclones in a 222-year period, according to research compiled by disaster historian Monowar Hossain Akhand. The 1970 Bhola Cyclone alone killed an estimated 300,000 to 500,000 people — still the deadliest tropical cyclone in recorded human history. The 1991 Cyclone Gorky killed 147,000. Twenty-six of the 35 deadliest tropical cyclones in world history have been Bay of Bengal storms. Forty-two percent of all tropical cyclone-associated deaths globally in the past two centuries occurred in Bangladesh.

And yet the more recent numbers tell a different story. Cyclone Sidr in 2007, a Category 4–5 equivalent storm with winds up to 260 km/h, killed approximately 3,400 people. Cyclone Amphan in 2020, an extremely severe cyclonic storm, killed 26 people in Bangladesh. The gap between 1970 and 2020 is not a gap in storm intensity — it is a gap in preparedness infrastructure, early warning systems, and community mobilization. Understanding that gap, and where it still falls short, is what cyclone preparedness in 2026 requires.

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When Cyclone Season Is in Bangladesh

Tropical cyclones strike Bangladesh in two distinct seasons. The pre-monsoon season runs from April to June, peaking in May. The post-monsoon season runs from October to December, peaking in November. Between these windows, the monsoon's atmospheric dynamics suppress cyclone formation over the Bay of Bengal, so July through September are relatively safer months for the coast. This seasonal pattern is well-established and has held consistently over decades: Cyclone Aila struck 25 May 2009, Cyclone Remal struck 26 May 2024, Cyclone Amphan struck 20 May 2020, Cyclone Sidr struck 15 November 2007, Cyclone Bulbul struck 9 November 2019.

In 2026, the pre-monsoon cyclone season runs from approximately April through June. The 2026 North Indian Ocean cyclone season has already seen activity: a low-pressure area formed over the Bay of Bengal on 7 January 2026, intensified into a depression on 8 January, and made landfall over Sri Lanka before weakening. The primary risk window for Bangladesh-affecting storms opens in late April and runs through June for pre-monsoon storms, and again in October through November for post-monsoon storms. Residents of the 13 sea-facing coastal districts should treat the period from 15 April to 30 November as the active preparation window for 2026.

Climate science is changing the frequency calculation. NASA research published in 2024 found that while the total number of tropical cyclones is expected to decrease globally due to warming, more intense cyclones are expected to become prevalent in the northern Bay of Bengal, particularly during the post-monsoon season. The research specifically identifies Bangladesh, India, and Myanmar as affected zones. A 2026 paper in npj Natural Hazards modelling storm-tide risk under future climate scenarios projects heightened storm surge risk for the Ganges-Brahmaputra-Meghna delta under mid-century conditions. Cyclone Remal in 2024 demonstrated this dynamic: its maximum wind speed was less than half that of Sidr, but its 36-hour duration and larger rotation diameter caused more widespread flooding and tidal surge than faster, more compact storms.

The 13 High-Risk Districts: Who Is in the Zone

Bangladesh has 13 sea-facing coastal districts that form the primary cyclone risk zone. These districts — Satkhira, Khulna, Bagerhat, Pirojpur, Barguna, Patuakhali, Bhola, Lakshmipur, Noakhali, Feni, Chittagong, Cox's Bazar, and the coastal areas of Barisal — are classified as the CPP (Cyclone Preparedness Programme) command area. They cover 37 upazilas and 322 unions that sit directly adjacent to the Bay of Bengal. According to the Bangladesh Bureau of Statistics, approximately 35 million people live within these districts — meaning roughly one in five Bangladeshis lives in the primary cyclone impact zone. When the wider area of risk is factored in, including river flooding and inland surge penetration, the affected population exceeds 90 million.

The highest mortality history concentrates in specific districts. Research analyzing 41 major cyclonic storms from 1970 to 2021 found that Chittagong, Patuakhali, and Barishal experienced the highest death rates across the dataset. At the upazila level, Sandwip upazila in Chittagong and Mirzaganj upazila in Patuakhali had the highest mortality rates of any single sub-district. Barguna district, where Cyclone Sidr's storm surge reached six meters in places, and Khulna, which bore the brunt of at least 18 cyclones in 17 years according to the Dhaka Tribune, are among the most consistently impacted zones. Cox's Bazar, home to the world's largest refugee settlement at Kutupalong, faces compounded risk: the Rohingya camps sit on hillsides that face both cyclone wind damage and landslide risk during cyclone-associated rainfall.

The Warning Signal System: What Each Number Means

Bangladesh uses a numerical danger signal system issued by the Bangladesh Meteorological Department (BMD) from the Cyclone Warning Centre. The system runs from 1 to 11 for maritime ports and 1 to 4 for river ports. Understanding these signals is the most basic preparedness requirement for anyone living in or visiting coastal Bangladesh during cyclone season.

Signal 1 (Distant Cautionary Signal): A low-pressure area or depression has formed in the Bay of Bengal. No cyclone has formed yet. Fishing boats should monitor weather bulletins. No evacuation is required. This signal means the Bay is active — residents in coastal zones should begin mentally preparing and checking their emergency supplies.

Signal 2 (Distant Warning Signal): The system has intensified. Fishing trawlers should return to port. Weather will deteriorate over the coming days but a direct hit is not yet confirmed. Begin checking cyclone shelter locations and ensuring household emergency kits are stocked.

Signal 3 (Local Cautionary Signal): The system is within range and likely to affect the coast within 36 to 72 hours. Fishing boats and cargo vessels should not leave port. Coastal communities should identify their nearest cyclone shelter, check its current condition, and prepare for possible evacuation. This is the last comfortable window for preparation.

Signal 4 (Local Warning Signal): Direct threat within 36 hours. River ports begin hoisting warning signals. Prepare to evacuate livestock, secure documents and valuables, move to a cyclone shelter or elevated ground if your home is in a low-lying or surge-prone area.

Signals 5, 6, 7 (Danger Signals of Escalating Intensity): The cyclone is forming and approaching. Signal 6 means a severe cyclonic storm is expected within 24 hours. Signal 7 indicates very severe intensity. Evacuation orders are issued for the most vulnerable zones. CPP volunteers begin door-to-door mobilization with megaphones. All residents in storm surge zones must evacuate by Signal 7 — waiting until Signal 10 or 11 is a life-threatening decision.

Signals 8, 9, 10, 11 (Great Danger Signals): These signals indicate extreme cyclone conditions — extremely severe to super cyclonic storm intensity — with landfall imminent within 12 to 24 hours. At Signal 10, maximum wind speeds exceed 200 km/h. At Signal 11, the highest category, landfall is hours away and conditions are catastrophic. If you are still in a storm surge zone at these signal levels, your life is in immediate danger.

The critical point that coastal residents and emergency planners emphasize consistently: evacuation must happen by Signal 6 or 7, not 10 or 11. Storm surge — the wall of ocean water pushed inland by a cyclone's rotation — kills faster and further than wind. The 1970 Bhola Cyclone killed most of its victims by storm surge, not wind. So did Sidr in 2007. By the time Signal 10 is issued, roads may already be flooded and movement impossible.

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The CPP: How Bangladesh Warns 35 Million People in 15 Minutes

The Cyclone Preparedness Programme, established in 1973 as a joint initiative of the Government of Bangladesh and the Bangladesh Red Crescent Society, is widely cited as one of the most effective community-based disaster warning systems in the world. It operates through a network of over 76,000 trained volunteers deployed across the 13 coastal districts, approximately half of whom are women. The volunteer network is organized into five functional groups per local unit: Warning Signal, Shelter, Rescue, First Aid, and Relief.

When BMD issues a cyclone warning, the system works with documented speed. Warning information from BMD can be disseminated to CPP volunteers and the public at risk in less than 15 minutes from the time of warning issuance to the beginning of evacuation orders. This speed is achieved through a layered telecommunications system: HF and VHF wireless stations at field levels, mobile phone contact between BMD and CPP district offices, and then physical volunteer deployment for door-to-door warning dissemination. In remote communities without reliable mobile network coverage — which includes many coastal chars and offshore islands — volunteers use megaphones mounted on boats or at mosque minarets to reach households that would otherwise receive no warning.

The CPP command area covers 3,291 units across 37 upazilas. The system is designed with a 30-hour lead time as the operational baseline: reliable cyclone forecasting allows 30 hours between forecast and expected landfall, within which CPP volunteers must complete warning dissemination and evacuation facilitation. This 30-hour window has been formalized in Bangladesh's National Early Action Protocol for Cyclones, developed with Bangladesh Red Crescent Society support and finalized in June 2024.

Digital innovation is being layered onto this network. The "Disaster Alert for BD" mobile app, deployed under a project supported by Practical Action and the World Bank, reached 38,643 direct beneficiaries as of late 2025. In a survey of 106 community members, 84 percent fully understood the early warning messages received through the app, and 92 percent reported taking proactive preparedness measures after receiving a warning. A CPP volunteer in Koyra upazila described receiving warnings from the app during Cyclone Remal in May 2024 and using it to independently verify timing before mobilizing thirty youth volunteers for evacuation assistance — without waiting for the CPP team leader's instruction.

Cyclone Shelters: Capacity, Location, and the Gap That Remains

Bangladesh has built more than 4,000 multipurpose cyclone shelters across the coastal zone, a number that has grown substantially since the 2007 post-Sidr reconstruction effort. Many are dual-purpose structures: school buildings reinforced to withstand winds above 260 km/h, with ramps for accessibility, elevated floors above anticipated storm surge levels, and storage capacity for emergency supplies. The Bangladesh Delta Plan 2100, approved by the government in 2018, commits approximately two and a half percent of GDP annually — around $6 billion — to coastal resilience infrastructure including shelter construction and coastal embankment maintenance.

Despite this investment, structural gaps remain. Older research estimated that approximately 73 percent of people in the most vulnerable coastal areas lived without adequate shelter access. The World Bank's Coastal Embankment Improvement Project has been upgrading 6,000 km of coastal embankments, but repair backlogs persist after each major storm — Cyclone Remal in 2024 damaged a 38 km stretch of Koyra embankment in Khulna, and only 15 km had been repaired by late 2024. The shelter capacity problem compounds for Cox's Bazar: the Rohingya camp population of approximately 1.2 million lives in temporary structures with limited access to formal cyclone shelters, and storm preparedness in the camps depends heavily on CPP volunteer coordination with UNHCR and camp management committees.

The practical rule for shelter access: every union in the 13 coastal districts has at least one designated cyclone shelter. Many have several. The CPP unit in your area knows the location and capacity of each shelter. If you do not know the location of your nearest cyclone shelter, the time to find out is now — not when Signal 6 is hoisted.

What to Prepare Before Cyclone Season Begins

The Bangladesh Meteorological Department and CPP recommend completing household preparedness before the peak pre-monsoon season window opens in late April. The preparation checklist that the CPP distributes through its volunteers covers several categories.

Emergency supplies: Store at minimum a three-day supply of dry food in sealed, waterproof containers — rice, lentils, dried fish, biscuits, and oral rehydration salts. Store at least 10 liters of clean drinking water per household member in sealed containers. Keep a battery-powered or hand-crank radio for receiving BMD bulletins — mobile networks fail during cyclone landfall and a radio may be the only functioning information source. Keep waterproof pouches containing your national ID card, land documents, and bank records. Post-cyclone, these documents determine access to relief and rebuilding assistance.

Structural preparation: Know the construction type of your home. Kutcha structures — mud or bamboo walls with tin roofs — are the most vulnerable to cyclone winds and surge. If your home is kutcha and in a low-lying area, your evacuation plan must prioritize leaving before Signal 7, not sheltering in place. Secure loose objects — tin sheets, tools, furniture, fishing equipment — that can become projectiles in high winds. If you have a well, cover and seal it against saline intrusion from storm surge.

Livestock: Animals cannot enter most cyclone shelters. Move livestock to elevated ground or elevated structures as early as possible — waiting until Signal 7 means livestock will be lost. Post-cyclone food security depends significantly on whether breeding stock survives, so early livestock protection is not just an economic calculation but a food security one.

Medications and health: Coastal communities face acute disease risk after cyclone landfall. Diarrhea outbreaks following Cyclone Aila in 2009 infected over 7,000 people within days. Water contamination, sanitation infrastructure collapse, and displacement into shelter crowding create rapid transmission conditions for diarrhea, typhoid, and skin infections. Maintain a stock of oral rehydration salts, water purification tablets, basic wound care supplies, and any prescription medications your household requires for at least seven days beyond cyclone landfall.

The Evacuation Decision: Why People Don't Go and Why That Kills Them

Research consistently identifies two failure modes in Bangladesh's cyclone preparedness system that still cost lives: false alarm fatigue, and the economic cost of evacuation. Both are structural problems that the CPP and BMD have not fully solved.

False alarm fatigue occurs when cyclone warnings are issued and the predicted storm weakens or changes track before landfall. Residents who evacuate and lose a day's income, return to find their home and livestock undamaged, and repeat this several times develop a rational distrust of the warning system. Studies in coastal Bangladesh found that residents in some areas did not follow evacuation orders because of prior false alarm experiences. BMD forecasts are acknowledged to be reliable for approximately 12 hours ahead but become less precise for longer lead times — meaning early warnings issued 48 to 72 hours before potential landfall carry genuine uncertainty that communities have learned to discount.

The economic cost problem is equally documented. Evacuation means leaving your home, your livestock, and often your stored food and livelihood tools unguarded in a community where theft is a real risk during emergency displacement. For fishing households, cyclone season evacuations mean losing fishing days at the peak of certain fish seasons. For agricultural households, leaving during a ripening or harvest period means crop loss regardless of whether the cyclone strikes. The CPP's community-based model has partially addressed this by building trust at the local level — communities that have longstanding relationships with their CPP volunteer leader show higher evacuation compliance than those served by unfamiliar volunteers.

The guidance from CPP and international disaster risk research is consistent: evacuate when ordered at Signal 6 or 7, regardless of prior false alarm experience. The asymmetry of outcomes is absolute. If you evacuate unnecessarily, you lose a day and some inconvenience. If you shelter in place during a direct hit on a storm surge zone, the historical probability of death is high. The 1991 Gorky Cyclone killed 147,000 people in a coastal belt that had early warning — the deaths were concentrated among those who did not evacuate.

After Landfall: The Second Wave of Risk

Cyclone mortality in Bangladesh does not end when the storm passes. In many major events, more deaths have occurred in the days and weeks following landfall than during the storm itself, due to waterborne disease, contaminated drinking water, failed embankments that keep flood water trapped after the storm, and delayed medical access for the injured.

The Khulna region has experienced this most acutely. Cyclone Aila in 2009 caused flooding that persisted for months in parts of Koyra upazila due to damaged embankments — families lived on embankment slopes without access to clean water or sanitation for extended periods. Cyclone Remal's 2024 landfall left a 38 km section of Koyra embankment damaged, of which only 15 km had been repaired by November 2024. Salinity intrusion from storm surge contaminates freshwater ponds and wells for months after a cyclone event — the freshwater crisis in the southwest coastal zone is a cumulative problem that each new cyclone deepens.

Immediate post-cyclone priorities at the household level: do not use well water or surface water without testing or treating, as storm surge salinates fresh water sources. Seek medical attention immediately for any wounds — wound infections in flood conditions progress rapidly. Report to your local UP (Union Parishad) or upazila disaster management committee for relief registration — the government's relief distribution system operates through formal registration, and unregistered households may not receive food, cash, and rebuilding materials that they are entitled to.

Where to Follow Cyclone Updates in 2026

The primary authoritative source for cyclone forecasts and warning signals for Bangladesh is the Bangladesh Meteorological Department (BMD), accessible at bmd.gov.bd. BMD issues Special Weather Bulletins during active cyclone events, updated every three hours as storm approach accelerates. The cyclone track page at the BMD website provides real-time signal status for each maritime and river port.

Bangladesh Television (BTV) and Bangladesh Betar (national radio) carry mandatory cyclone bulletins during active warning periods. BTV is the single most widely accessible broadcast medium in coastal areas, and BMD bulletins are transmitted on a mandatory basis during Signal 3 and above. For residents of areas without reliable mobile internet access, a battery-powered AM/FM radio that can receive Bangladesh Betar is more reliable during an active cyclone event than a smartphone.

The Disaster Alert for BD mobile app provides real-time warnings integrated from BMD data. The CPP volunteer network in your union is the most locally specific warning source — they have ground-level information about storm surge projections for your specific location, shelter capacity status, and evacuation route conditions that no national broadcast can match. If you live in one of the 13 coastal districts, know your local CPP volunteer's name and number before April 15.

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