Hurricane Irma caused severe damage and destruction in the Lesser Antilles.

Preparations

In Antigua and Barbuda, residents safeguarded their homes and cleaned up their properties in anticipation of strong winds. Emergency crews were put on standby at public shelters and hospitals by September 5 to assist with any evacuations. Expecting a direct hit, more than half of the residents on Barbuda took shelter, and relief supplies were preemptively mobilized. The National Emergency Management Organization on Saint Lucia urged small craft operators and swimmers to be mindful of forecasts for high surf. Small Craft Warnings and High Surf Advisories were hoisted for Dominica, where residents were urged to remain vigilant of the potential for high waves, landslides, and flooding.

In Guadeloupe, low-lying and cliff-edge homes were evacuated at the threat of flooding and erosion. Schools and public businesses closed on September 5 and 6. Hospitals stocked up on three days' worth of supplies and checked the functionality of their generators. Of the island's 32 communes, 22 activated their emergency plans; 1,500 people were urged to take shelter. The island sustained relatively minor damage and became the base for relief efforts on Saint Martin and Saint Barthélemy. Though the core of the hurricane was expected to remain north of the island, a yellow alert was issued for Martinique due to the likelihood of rough seas. The island dispatched relief supplies and military reinforcements to its neighboring islands of Guadeloupe, Saint Martin. and Saint Barthélemy, which faced a greater risk of a direct impact.

From a relatively early stage of its development, Irma was predicted to travel close to, or over, the British Virgin Islands. However, the late stage intensification of the storm was less well anticipated. As little as two days before the storm struck, the BVI Department of Disaster Management were predicting maximum expected wind speed of - on the boundary between a Category 2 and Category 3 hurricane. Over the course of 5 September 2017 Hurricane Irma rapidly intensified until it had strengthened well beyond sustained wind speeds required for classification as a Category 5 hurricane, into the strongest hurricane ever recorded over the open Atlantic Ocean (excluding the Gulf of Mexico and Caribbean Sea). Although the BVI government recommended the full evacuation of Anegada, about 180 people stayed behind, while the rest went to Tortola.

Impact Antigua and Barbuda

The eyewall of the hurricane moved over Barbuda at its record peak intensity early on September 6; a weather station observed a wind gust of . The same station also recorded a minimum barometric pressure of . The exact state of the island remained unclear for hours after Irma's passage, as downed phone lines ceased all communication with nearby islands. Later that afternoon, Prime Minister Gaston Browne surveyed the territory by helicopter, revealing an effectively uninhabitable island. Irma damaged or destroyed 95% of the structures on Barbuda, including its hospital, schools, and both of its hotels; it completely flattened some residential blocks while submerging others. The destruction rendered the island's sole airport and much of its infrastructure inoperative—including water and telecommunication services—which further hampered relief efforts. Property damage on Barbuda ranged from $150 million to $300 million. A total of three storm-related deaths were reported on the island.

In addition to the catastrophic impact on Barbuda's human residents, concern turned to the storm's effects on the island's wildlife. The island's only endemic bird, the near-threatened Barbuda warbler, numbered less than 2,000 individuals prior to the hurricane. For some time it was unknown if the warbler survived the hurricane or its aftermath; however within a few months it was confirmed that not only did the species survive, but most of the birds survived the storm. Barbuda's Codrington Lagoon, home to the largest colony of magnificent frigatebirds in the Caribbean, with an estimated 2,500 nesting pairs, was also inundated by the storm surge.

Remaining just outside of Irma's strongest windfield, Antigua sustained less severe damage, in the form of leveled roofs and fences, downed power poles and lines, and uprooted trees. Some street flooding also took place in low-lying areas. Three people were treated for minor storm-related injuries. Forensic disaster analysts from the Center for Disaster Management and Risk Reduction Technology (CEDIM), a Germany-based risk management agency, estimate that economic losses for Antigua and Barbuda will exceed $120 million.

Saint Martin

On the morning of September 6, Irma's center crossed the island of Saint Martin while the storm was at peak intensity, sweeping away entire structures, submerging roads and cars, and triggering an island-wide blackout. Irma's extreme winds ripped trees out of the ground and sent vehicles and debris from damaged structures scattered across the territory. On the French side of Saint-Martin, entire marinas around Marigot were left in ruins, littered with the stranded remnants of boats that had smashed into each other. A hotel caught on fire, but dangerous conditions and impassable roads prevented firefighters from putting out the blaze. Another hotel lost nearly all of its ground floor. Media images depicted devastated room interiors with furniture hurled around after the winds had shattered their windows. Irma killed four people on the French side of the island and injured 50 others, one of whom was in critical condition. As many as 95% of the buildings there were damaged to some degree; 60% of those were totally uninhabitable. Estimates from CEDIM indicate a minimum of $950 million worth of economic losses. Total losses exceeded €3.5 billion (US$4.17 billion).

A similar situation unfolded in Sint Maarten, Saint Martin's Dutch half, as intense winds ripped through buildings and lifted vehicles aloft "as if they were matches". The hurricane wreaked havoc on Princess Juliana International Airport, with "huge chunks of the building [strewn] across the runway and a jet bridge snapped in half." It demolished or severely damaged about 70% of Sint Maarten's houses, forcing thousands of residents into public shelters. There were 4 deaths and 23 injuries, 11 of which were serious, in the Dutch territory. Irma is considered the worst natural disaster to hit Sint Maarten; the extent of its damage far exceeded that of any previous hurricane. Total damages were estimated at €2.5 billion (US$2.98 billion).

Saint Barthélemy

Irma left widespread destruction and disastrous flooding along its path over the French island of Saint Barthélemy, southeast of Saint Martin. Describing the extent of the destruction, one local compared it to "a bomb that burned all vegetation," while another said that it were as if the hurricane had effectively "erased the island from the map". Violent seas swept away entire coastal establishments, with one hotel being stripped of all but its foundation. Streets in the capital of Gustavia were turned into rushing rivers, which carried away vehicles and pieces of furniture. The island's fire station was inundated with up to of flood waters. With scores of homes and much of the infrastructure destroyed, the majority of the island's population was left stranded and without water, electricity or phone service. The associated economic losses could exceed $480 million according to CEDIM's analysts.

Preliminary assessments from the French government indicate that Hurricane Irma caused a combined €1.2 billion (US$1.43 billion) in insured losses across the French territories of Saint-Martin and Saint Barts. This total covered private property such as homes, vehicles and businesses (including lost revenue); the extent of the damage to infrastructural and public facilities remains undetermined. Nonetheless, this made Irma one of the costliest natural disasters to hit the French Republic in 50 years.

On January 30, 2018, roughly five months after Irma, an analysis was published indicating that an anemometer on the island recorded an unofficial gust to before failing.

Anguilla The British Overseas Territory of Anguilla saw the eyewall of the storm pass over it on September 6. Many homes and schools were destroyed, and the island's only hospital was badly damaged. The devastation was particularly severe in East End, where the winds uprooted scores of trees and power poles and demolished a number of houses. In The Valley, the island's capital, the hurricane blew out the windows of government buildings. Rough seas inflicted heavy damage upon several bays and harbors, and a seaside restaurant was completely eradicated. About 90% of roads were left impassable. The island's air traffic control tower was damaged, exacerbating the already poor communication with the island. One death was reported on the island. Estimates of losses on the island total at least $190 million.

British Virgin Islands

Damage in the British Virgin Islands was extensive. Numerous buildings and roads were destroyed on the island of Tortola, which bore the brunt of the hurricane's core. Four people were confirmed dead. The Territory also experienced an abnormally high number of deaths in the months of September to December 2017, after the passage of the hurricane. Along Cane Garden Bay, the storm surge submerged several seaside bars and a gas station. Satellite images revealed many of the island's residential zones had been left in ruins. The hurricane passed over Necker Island, also causing severe damage and destroying the mansion of Richard Branson. By the time the storm hit the British Virgin Islands, it had intensified to such a level as to be detected on seismometers calibrated for earthquakes.

The estimated damage to property in the British Virgin Islands was initially calculated to be US$3.6 billion. Approximately 85% of housing stock, consisting of 4,200 homes, were damaged or destroyed in the territory. Roads across the territory were left impassable. Communities were essentially cut-off from each other and the wider world. Telecommunications was rendered virtually non-existent by the destruction of the cellular telephone network and the almost total loss of telephone poles for landlines. Most homes and businesses were destroyed on the island of Jost Van Dyke, the smallest of the B.V.I.'s four main islands. Irma damaged the Elmore Stoutt High School on Tortola, causing students to move to a temporary building. The Balsam Ghut prison was heavily damaged, allowing some prisoners to escape. The building which housed the Department of Disaster Management was almost totally destroyed in the storm. The Governor, Gus Jaspert, who had only been sworn into office 13 days previously, declared a state of emergency - the first time this has ever happened in the Territory. After the storm, restoration of electricity took approximately 5 months.

U.S. Virgin Islands

Irma's effects in the U.S. Virgin Islands were most profound on Saint Thomas, where at least of rain fell, and on Saint John. Saint Thomas island suffered widespread structural damage, including to its police station and airport. Patients from the fourth and third floors of Charlotte Amalie's hospital had to be relocated to lower floors due to flooding from roof leaks. Three deaths were attributed to Irma on the island. On nearby Saint Croix, there were communication issues and some damage to the infrastructure. Saint John lost access to ferry and cargo services, along with access to the local airport. Due to its normal reliance on electricity from Saint Thomas, the island was left without power. Total damage from the three islands was at least $1.1 billion.

Rest of the Lesser Antilles