Hurricane zones are the warm tropical seas where tropical cyclones form, traditionally divided into seven basins: the North Atlantic (with the Caribbean and Gulf of Mexico), the eastern North Pacific, the western North Pacific, the North Indian Ocean, the South-West Indian Ocean, the Australian region and the South Pacific. The same storm is called a hurricane in the Atlantic and north-east Pacific, a typhoon in the north-west Pacific and a cyclone in the Indian Ocean and South Pacific. Storms need sea water of at least 26.5 °C to a depth of about 50 m and usually form at least 500 km from the equator, where the Coriolis effect is strong enough to set them spinning. About 86 reach tropical-storm strength worldwide each year, and the western North Pacific is the busiest basin, averaging about 25.7 named storms a year. The coastlines most exposed include the Philippines, southern China, the US Gulf Coast, the Caribbean, Bangladesh and eastern India, Mozambique and Madagascar, and northern Australia.
The six places below each sit in a different zone, and each storm shows one rule about how these zones work.
Leyte and Samar, Philippines: Typhoon Haiyan in November 2013
The western North Pacific, the stretch of ocean north of the equator and west of the International Date Line including the South China Sea, produces about a third of all tropical cyclone activity on Earth. It sees storms all year round, with activity at its lowest in February and March. Storms here strike China, Taiwan, Japan, the Koreas, Vietnam, Guam and above all the Philippines, which takes an average of six to seven tropical cyclone landfalls a year. The coast of China sees the most landfalling tropical cyclones of any coastline in the world.
Typhoon Haiyan, known in the Philippines as Super Typhoon Yolanda, began on 2 November 2013 as a low-pressure area several hundred kilometres east-southeast of Pohnpei in Micronesia. Tracking generally westward through conditions that favoured development, it intensified rapidly from 5 November. The US Joint Typhoon Warning Center estimated one-minute sustained winds of 315 km/h on 7 November, and the Philippine weather agency PAGASA put ten-minute sustained winds at 235 km/h when it struck Guiuan in Eastern Samar.
The wind was not the main killer. In Tacloban on Leyte, a storm surge of 5.2 m wrecked the airport terminal up to its second storey, and the city administrator estimated that roughly 90 percent of the city was destroyed. The national disaster council confirmed 6,300 deaths, 5,902 of them in the Eastern Visayas, and the storm destroyed 550,928 houses. Investigators pointed to Tacloban's position between Samar and Leyte and its large population living in low-lying areas.
New Orleans and the Gulf of Mexico: Hurricane Katrina in August 2005
The North Atlantic basin covers the open Atlantic, the Caribbean Sea and the Gulf of Mexico. On average it produces 14 named storms a season, of which 7 become hurricanes and 3 become major hurricanes, and the official season runs from 1 June to 30 November, with a climatological peak around 10 September. Many of the most intense storms are Cape Verde-type hurricanes that form off West Africa and cross the whole ocean before reaching the Caribbean or the US coast. Some seasons bring a single storm; others bring more than twenty-five.
Hurricane Katrina formed near the Bahamas on 23 August 2005, crossed southern Florida, and then entered the Gulf of Mexico, where it intensified rapidly over warm Gulf water. Early on 28 August it peaked as a Category 5 storm with winds of 280 km/h and a central pressure of 902 mbar. It weakened to Category 3 before landfall near Buras-Triumph, Louisiana, on 29 August, but its storm surge was already built. About 80 percent of New Orleans flooded, largely because of engineering flaws in the federally built levee system around the city. Katrina killed 1,392 people and caused an estimated $125 billion in damage, the costliest tropical cyclone in US history. Our guide to the hurricane season explains why late August and September are so dangerous in the Gulf.
The Bay of Bengal and the Bhola Cyclone of November 1970
The North Indian Ocean is the least active basin, with only about four to six storms a year, and the Bay of Bengal produces five to six times as many as the Arabian Sea. Its season has an unusual double peak, in April and May before the monsoon and in October and November after it. During the monsoon itself, strong vertical wind shear between the surface monsoon low and the upper-level high tears developing storms apart. The same shear explains why no tropical cyclones form in the Red Sea, even though its water is warm enough all year.
Few storms, but the deadliest on record. The 1970 Bhola cyclone formed over the central Bay of Bengal on 8 November, reached winds of 185 km/h on 10 November and struck East Pakistan, now Bangladesh, and India's West Bengal on 12 November. At least 300,000 people died, possibly as many as 500,000, mostly drowned by the storm surge that swept the low islands of the Ganges Delta. In Tazumuddin upazila, more than 45 percent of a population of 167,000 were killed. The government's slow relief effort fed the anger behind the Awami League's landslide in the election a month later and the Bangladesh Liberation War of 1971. Extremely high population densities in the low-lying Ganges and Ayeyarwady deltas are why the deadliest tropical cyclones on record have struck this basin; our guide to Indian Ocean cyclones covers the basin in more detail.
Beira, Mozambique: Cyclone Idai in March 2019
South of the equator the rules flip: storms spin clockwise rather than anticlockwise and the season falls in the southern summer. The South-West Indian Ocean, between the African coast and 90°E, is monitored mainly by Météo-France's regional centre on La Réunion. About nine storms a year reach tropical-storm strength there, and about five go on to hurricane strength. Storms that slip into the Mozambique Channel, between Madagascar and the mainland, can strengthen over warm water before reaching the African coast.
Cyclone Idai began as a tropical depression off Mozambique on 4 March 2019, crossed the coast, wandered over land for five days, then re-entered the Mozambique Channel and intensified to peak winds of 195 km/h on 14 March. It made landfall near the port city of Beira on 15 March and then stalled, pouring rain over Mozambique, Zimbabwe and Malawi. More than 1,500 people died, making Idai the deadliest tropical cyclone recorded in the South-West Indian Ocean and the second-deadliest in the Southern Hemisphere, after the 1973 Flores cyclone in Indonesia.
Darwin, Northern Territory: Cyclone Tracy at Christmas 1974
The Australian region, between 90°E and 160°E, sees about seven cyclones a year. According to the Australian Bureau of Meteorology, the most frequently hit stretch of coast is between Exmouth and Broome in Western Australia, and Cyclone Vance in 1999 produced the highest wind speed recorded in an Australian town, about 267 km/h. More storms drift in from neighbouring basins, such as the South Pacific, in some years.
Cyclone Tracy was tiny. On 21 December 1974 satellite images showed a new circulation near 8°S, 135°E, and on 24 December it turned unexpectedly towards Darwin. Gusts reached 217 km/h before the instruments failed. Tracy killed 66 people and destroyed more than 70 percent of the city's buildings, including 80 percent of its houses; more than 25,000 of Darwin's 47,000 residents were left homeless and over 30,000 were evacuated. It held the record for the smallest tropical cyclone by diameter of gale-force winds for 34 years. Darwin was rebuilt to a stricter cyclone building code, a lesson for every city in a cyclone zone.
Santa Catarina, Brazil: Catarina and the Empty South Atlantic
The clearest proof of the rules is the zone that lacks hurricanes. The South Atlantic is not one of the seven basins: consistently strong wind shear and a weak Intertropical Convergence Zone keep tropical storms there rare. The handful on record include an Angola tropical storm in 1991, Tropical Storm Anita in 2010, Iba in 2019 and Akará in 2024. Since 2011 the Brazilian Navy Hydrographic Center has named them.
Catarina, in March 2004, is the only one known to have reached hurricane strength. It began as an extratropical system, gained tropical characteristics in slightly below-average wind shear and above-average sea temperatures, and made landfall on 28 March between Passo de Torres and Balneário Gaivota in Santa Catarina state with one-minute winds of about 160 km/h. It was the first tropical cyclone to make landfall in Brazil since reliable records began, so neither buildings nor people were prepared for one; Catarina destroyed about 1,500 homes and damaged about 40,000 others.
Europe sits just outside the Atlantic zone in the same way. Hurricane Vince, which came ashore in south-west Spain as a tropical depression in October 2005, and Subtropical Storm Alpha, which hit Portugal in September 2020, are the only systems known to have reached mainland Europe as tropical or subtropical cyclones since the US records begin in 1851.
The equator is the other empty zone. Within about 500 km of it the Coriolis force is too weak to organise rotation, so storms almost never form there, while storms that drift poleward over water much cooler than 26.5 °C, or into strong wind shear, lose their warm core and weaken. Put together, those limits draw two bands of risk either side of the equator. For the step-by-step physics behind that heat engine, see our explainer on how hurricanes form.