What is a cyclone? Definition, causes and how to help survivors

A cyclone can go by many names, and in Jamaica, its name was Hurricane Melissa in 2025. When Hurricane Melissa hit Jamaica as a Category 5 storm, it became one of the strongest storms ever recorded in the Atlantic Ocean. The small community of Chester Castle was left in ruins.

Norma, 67, stood where her home used to be. "This was my home. Kitchen, room. All of it’s gone." Her daughter Shantel and grandson Zyair, 18 months old, lived in that home before the storm hit. Shantel says, “Zyair loved TV. He would point at the screen and say, ‘Tee tee tee.’” Now the television lies buried under rubble. “He doesn’t understand,” she says.

Storms like Melissa go by different names around the world. According to the World Meteorological Organization, in the Atlantic, this is a hurricane. In the Philippines and Japan, the same storm is a typhoon. In Sri Lanka, Mozambique and Australia, it is a cyclone.

Whatever the name, the damage looks the same: broken homes, lost belongings and children who cannot understand why their world changed overnight.

Let’s explore what a cyclone is, why cyclones form and how World Vision helps families like Norma’s rebuild once the storm passes.

What is a cyclone?

According to the Australian institute of Marine research (AIMS), Cyclones are large revolving tropical storms caused by winds blowing around a central area of low atmospheric pressure. The whole system can stretch hundreds of kilometres wide.

The word cyclone comes from a Greek word meaning coil of a snake. It describes the way the storm twists as it spins. Cyclone, hurricane and typhoon all describe the same kind of storm. The only real difference is where it forms.

Scientists also sort tropical cyclones by strength. The Saffir-Simpson scale runs from Category 1 to Category 5 based on sustained wind speed.

• Category 1: winds of 119 to 153 kilometres per hour. Some damage: roof shingles and siding can peel off, large branches snap, and power outages are common.
• Category 2: winds of 154 to 177 kilometres per hour. Extensive damage: shingles tear away and siding cracks or breaks off, shallow-rooted trees topple, and neighbourhoods can lose power for several days.
• Category 3: winds of 178 to 208 kilometres per hour. Devastating damage: even sturdy homes can lose sections of their roofing, and clean water and electricity may be cut off for days or weeks. This is where a storm crosses into “major” territory.
• Category 4: winds of 209 to 251 kilometres per hour. Catastrophic damage: entire roof structures can give way and walls can come down, leaving communities cut off for weeks or months.
• Category 5: winds of 252 kilometres per hour or higher. Catastrophic damage: most homes in the storm’s path can be destroyed outright, leaving communities unlivable for months. Hurricane Melissa reached this level.

Hurricane Melissa reached Category 5, the highest level on the scale, with winds strong enough to flatten well-built homes. Governments and aid groups use this category system to judge how much warning time and how many resources a response will need.

Scientists also group cyclones into four broad types: tropical, subtropical, extratropical and polar. Tropical cyclones form over warm ocean water and are the kind that hit Jamaica, Sri Lanka and Mozambique. The other three form in cooler water or at higher latitudes and behave differently.

Inside a cyclone: the eye, eyewall and rainbands

Every mature cyclone has three main parts.

1. The eye sits at the centre. It is a calm, clear patch of low pressure, often 30 to 65 kilometres wide. At its widest, that’s roughly the straight-line distance between Hamilton and downtown Toronto.
2. The eyewall surrounds the eye. This ring holds the storm’s strongest wind and heaviest rain.
3. Rainbands spiral outward from the eyewall. These bands can bring flooding rain and gusty wind hundreds of kilometres from the centre, long before the eye arrives.

This structure explains why a cyclone can flood a region days before its strongest winds hit, and why the weather can turn suddenly calm as the eye passes overhead.

Meteorologists track this structure using satellites and aircraft that fly directly into the storm. Their forecasts give coastal communities crucial time to prepare before landfall.

How do cyclones form?

• Warm ocean water. The sun heats the ocean surface, and warm, moist air rises from the water, leaving lower pressure behind it. Cooler air rushes in to take its place, warms up in turn, and rises too, building a tall column of spinning cloud. The water needs to stay at least 27 degrees Celsius for this cycle to keep going, which is why cyclones form most often near the equator, according to the US National Oceanic and Atmospheric Administration.

• Moist air. Humid air carries the energy that feeds the storm as it grows.
• Low wind shear. When winds at different heights blow at similar speeds, the storm stays organized instead of being torn apart.
• Distance from the equator. The Earth’s rotation bends rising air into a spin, called the Coriolis effect. A cyclone needs enough distance from the equator for that effect to work, but not so much that the ocean turns cold.
• An existing weather disturbance. Most cyclones start as a small cluster of thunderstorms that slowly grow stronger.

The effects of cyclones on children and families

Cyclones do more than damage buildings. They interrupt entire childhoods.

Wind is often not the most dangerous part of a cyclone. Storm surge and inland flooding cause most cyclone deaths worldwide, because water rises faster than people expect and can cut off entire communities within hours.

Cyclone Ditwah struck Sri Lanka in late 2025, triggering flooding and landslides across the country at the same time. In Karachchi, all 35 Grama Niladhari divisions (local administrative areas) were affected, and 1,796 families were displaced from their homes.

World Vision Lanka set up five safety camps for displaced families in Karachchi. Teams also delivered dry rations to 58 families in each of two nearby divisions, Vivekananthanagar and Krishnapuram.

In Kandawalai, a collapsed bridge cut off the whole area. With support from World Vision Canada and World Vision Italy, relief teams still found ways to bring in dry rations and essential household items.

Farther south, in Mozambique, Cyclone Chido tore through Cabo Delgado province. It destroyed 196 classrooms and 78 health facilities. For children, that often means no school and no nearby medical facilities for months after the storm passes.

In many lower-income countries, families have fewer resources to rebuild after a storm like this. A flooded field or a lost fishing boat can mean months without stable income, and children usually feel that strain first, through missed meals or missed school.

Are cyclones getting worse?

Yes, and warmer oceans are the reason.

A 2024 study found that human-caused ocean warming raised the wind speeds of Atlantic hurricanes by an average of 19 miles per hour between 2019 and 2023, according to Climate Central.

Satellite data also shows more Category 5 storms in recent decades than in the past, according to NOAA’s Geophysical Fluid Dynamics Laboratory. Some hurricane scientists now argue the five-category scale is not enough.

A 2024 paper proposed adding a Category 6 for storms with sustained wind above 192 miles per hour. That’s because a warming climate makes storms of that strength more likely in the future.

Rising sea levels add another layer of risk, since the same storm surge now reaches farther inland than it would have several decades ago.

This trend matters most for families in coastal and low-lying areas. They are often the least prepared for a stronger storm and the least able to recover financially once it passes.

That is one reason World Vision invests in disaster risk reduction long before a storm forms, not only relief after it hits.

How to stay safe if a cyclone is coming

Cyclones move over water for days before reaching land, which usually gives forecasters time to issue clear warnings. What you do with that warning time matters most. For example, if you know a cyclone will hit in five days, that gives you five crucial days to prepare. Here is what to do during that time:

• Know your risk. Find out if you live in a low-lying or flood-prone area and learn about your community’s evacuation routes ahead of time.
• Prepare a basic kit. Pack water, non-perishable food, a flashlight, a battery-powered radio, first aid supplies and copies of important documents in a waterproof bag.
• Follow official warnings. Leave early if local authorities tell you to evacuate, rather than waiting to see how bad the storm gets.
• Stay away from floodwater. Even shallow, fast-moving water can sweep away an adult or a vehicle. Never drive or walk through it.
• Check on neighbours. Older adults, people with disabilities and families with young children often need extra help to evacuate safely.

These steps will not stop a cyclone from forming, but they can make the difference between a close call and a tragedy.

How World Vision is helping right now

Whether it’s a cyclone, hurricane or a severe storm, our response is the same. World Vision responds before, during and after a disaster hits.

In Jamaica, teams are distributing hygiene kits, bedding, flood cleanup kits, tarpaulins and Crisis Relief Boxes with enough food for a family for one week.

Mobile water treatment systems are also being set up to purify contaminated water, with local residents trained to keep the systems running after international staff leave, according to World Vision’s relief update for Jamaica.

In Sri Lanka, the World Vision Lanka Karachchi Area Programme team is coordinating with local Divisional Secretariat authorities to reach displaced families in all five camps and beyond, a response supported in part by Government of Canada funding to World Vision Canada.

A tropical storm is an earlier, weaker stage of the same system, before wind speeds reach cyclone or hurricane strength. The flooding rain can be just as damaging, which is what happened when Tropical Storm John hit Mexico, and World Vision responded there too.

Across all four countries, the pattern is the same: get people to safety first, then meet their most urgent needs for food, clean water and shelter, before starting the longer work of rebuilding.

You can help families recover faster. A gift to World Vision’s emergency response fund reaches families facing disasters like these directly.

Cyclones will keep forming. With support like yours, families such as Norma’s do not have to face the rebuilding alone.