The 2017 hurricane season was record-shattering, fueled by abnormally warm ocean water and a particularly conducive weather pattern over the Atlantic. It wasn't just the most active – it was also the most expensive on record in U.S. history. Although final costs may not be known for years, estimates suggest the tab will run beyond $200 billion.

Four notable storms from the 2017 season had names that will no longer be used for hurricanes, according to the U.N. World Meteorological Organization: Harvey, Irma, Maria and Nate.

Since 1979, the WMO has been using a six-year name rotation. Within a given hurricane season, male and female names alternate, then the following year, the gender ordering is staggered (for example, Ana and Bill one year, Alex and Bonnie the next, etc).

Unless a name is retired, the exact same list of names is used again six years later. However, if a storm gains notoriety because of its strength, number of deaths or damage, the WMO may retire that name from future use. For example, Katrina, Sandy and Isabel are all names that have been retired from the list.

Harvey, Irma, Maria and Nate will join the list of exceptional hurricane names. They will be replaced by Harold, Idalia, Margot and Nigel.

Hurricane Harvey kicked off the season in late August. The Category-4 hurricane slammed into Texas with 100-mph winds, but its torrential rainfall, up to 60 inches, and flooding was far more destructive. About 33 trillion gallons of water fell out of Harvey, most of which landed in a swath from Houston to Southwest Louisiana. Some estimates place Harvey ahead of Hurricane Katrina in damages – about $180 billion.

Just weeks later after scouring the Caribbean, Hurricane Irma made landfall in Key West, Florida, and then Marco Island in September. It was the first major hurricane to make landfall in Florida since 2005.

Irma knocked out power to as many as 16 million people across the Southeast, according to recent estimates from utility companies. The vast majority of these outages occurred in Florida, which was noticeably darker on satellite imagery as Irma pulled away from the state.

Hurricane Irma did upward of $65 billion in damage, mainly in the Virgin Islands and the Southeast United States.

No storm in 2017 was as devastating as Hurricane Maria was to Puerto Rico. It claimed the lives of just over 100 people. More than three months after Maria hit, more than half of the island's 3.3 million population still did not have power.

The official death toll remains artificially low according to an investigation by The New York Times, which found that the number of hurricane-related deaths probably exceeds 1,000. The governor of Puerto Rico ordered a recount of the death toll in mid-December.

Hurricane Nate rounds out the list, the ninth hurricane of the season. Nate developed in the Southern Caribbean and tracked north into the Gulf of Mexico. On Oct. 8, the hurricane made landfall as a Category 1. The storm did around $800 million in damage and killed 45 people in Central America and the United States.

The idea of permanently retiring names began after the 1954 hurricane season when Carol, Edna and Hazel ravaged the East Coast. Since that fateful year, 88 names have been retired, and those beginning with "I" make up the majority of them (11).

"I"-name storms tend to coincide near the average peak of the hurricane season. With ocean temperatures warm and hostile winds shear, conditions are prime for hurricane development. So it's not surprising that these storms are the most-retired.

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The Capital Weather Gang's Brian McNoldy contributed to this story.