As Super Typhoon Nepartak hits Taiwan and China, we explore how these tempests form and the risks they pose to people.

A massive “super typhoon” named Nepartak is bearing down on China and Taiwan. The giant storm is expected to make landfall on Taiwan’s east coast early Friday and hit China Saturday.

To be considered a super typhoon, a storm must have sustained winds above 150 miles (241 kilometers) per hour, and Nepartak “threatens all Taiwan” with strong winds and heavy rain, according to the island’s Central Emergency Operation Center.

It may sound confusing, but hurricanes, typhoons, and cyclones are all different names for the same type of storm. The difference is simply their location.

The storms that rage across the western Pacific Ocean (in the Eastern Hemisphere) are called typhoons, while the ones spawned in the Atlantic and eastern Pacific (the Western Hemisphere) are called hurricanes. Those born in the South Pacific and Indian Ocean are known as cyclones.

Hurricanes are named after Hurrican, a Caribbean god of evil. “Typhoon” is thought to originate from Persian and/or Chinese words that referred to strong storms.

Collectively, hurricanes, typhoons, and cyclones are known as “tropical cyclones.” They can span an area up to 1,000 miles (1,600 kilometers) in diameter.

To classify as a cyclone a storm must reach wind speeds of at least 74 miles per hour (119 kilometers per hour). If a storm’s winds reach speeds of 111 miles per hour (179 kilometers per hour), it is upgraded to an intense hurricane or typhoon.

And although Atlantic hurricanes get the lion’s share of media coverage in North America, those storms actually only account for about 11 percent of all tropical cyclones, Kerry Emanuel, an atmospheric scientist at the Massachusetts Institute of Technology, previously told National Geographic.

It’s That Time of Year

Globally, the tropical cyclones develop most often in late summer, when there is the greatest difference in temperature between the air and water. Worldwide, May is the least active month and September is the most active. In the Atlantic, a distinct hurricane season persists from about June 1 to November 30, after which air and water get too cool for the storms to develop.

Parts of the western Pacific are warm enough for the storms to develop at any time during the year, although the summer and early fall are still the most common periods.

No matter what the storms are called, they all need the same things—an atmospheric disturbance to generate storm clouds, surface ocean temperatures above 80°F (27°C), and very little vertical difference in atmospheric wind speeds. Beyond that, scientists are still trying to understand what triggers them, MIT’s Emanuel said.

How Storms Work

Once a storm is going, it is fueled by the evaporation of water into the air. Warm ocean waters feed that evaporation, cooling the immediate area and sucking more heat to the center of the storm. This sets up a cycle that keeps running until one or more of several factors stop it.

Those factors can include high wind shear, which can break up the storm or slow it down by blasting it with dry air. When the storms make landfall, they lose their ability to evaporate large amounts of water. Similarly, the churning winds can drag up cold water from the ocean deep, which results in less evaporation potential. (See what made Hurricane Patricia so powerful.)

The storms are categorized by the strength of their winds, although the wind itself often isn’t the most deadly part of the tempest. Storm surges—pulses of water pushed by the advancing cyclone—often result in coastal flooding that causes drowning and collapse of structures.

Surges were responsible for much of the devastation caused by Super Typhoon Haiyan in the Philippines in November 2013 (the storm was called Yolanda there). Haiyan was one of the largest and strongest storms ever recorded, with winds that reached 196 miles (315 kilometers) per hour. Storm surges as high as 25 feet (7.6 meters) washed away buildings, ripped up vegetation, and killed over 6,000 people.

Such powerful storms, such as Katrina, may become more likely thanks to warming of the air and water through climate change, Emanuel warns.