Hurricane Ida was a deadly and destructive Category 4 Atlantic hurricane that became the second-most damaging and intense hurricane to make landfall in the U.S. state of Louisiana on record, behind Hurricane Katrina in 2005. In terms of maximum sustained winds at landfall (150 mph (240 km/h)), Ida tied 2020's Hurricane Laura and the 1856 Last Island hurricane as the strongest on record in the state.^[1] The storm also caused catastrophic flooding across the Northeastern United States. Ida is the sixth-costliest tropical cyclone on record, having caused at least $50.1 billion (2021 USD) in damages,^[2][3] of which $18 billion was in insured losses in Louisiana, and of which $100 million was in Cuba, $584 million dollars in agriculture damage, surpassing Hurricane Ike of 2008. CoreLogic estimated that Ida caused an estimated $16 to 24 billion in flooding damage in the Northeastern United States, making it the costliest storm to hit the region since Hurricane Sandy in 2012,^[4] with an estimated $44 billion dollars in Insured loss.^[5] The ninth named storm, fourth hurricane, and second major hurricane of the 2021 Atlantic hurricane season, Ida originated from a tropical wave in the Caribbean Sea on August 23. On August 26, the wave developed into a tropical depression, which organized further and became Tropical Storm Ida later that day, near Grand Cayman. Amid favorable conditions, Ida intensified into a hurricane on August 27, just before moving over western Cuba. A day later, the hurricane underwent rapid intensification over the Gulf of Mexico, and reached its peak intensity as a strong Category 4 hurricane while approaching the northern Gulf Coast, with maximum sustained winds of 150 mph (240 km/h) and a minimum central pressure of 929 millibars (27.4 inHg). On August 29, the 16th anniversary of Hurricane Katrina, Ida made landfall near Port Fourchon, Louisiana, devastating the town of Grand Isle. Louisiana. Ida weakened steadily over land, becoming a tropical depression on August 30, as it turned northeastward. On September 1, Ida transitioned into a post-tropical cyclone as it accelerated through the northeastern United States, breaking multiple rainfall records in various locations before moving out into the Atlantic on the next day. Afterward, Ida's remnant moved into the Gulf of St. Lawrence and stalled there for a couple of days, before being absorbed into another developing low on September 4.

Ida knocked down palm trees and destroyed many homes in Cuba during its brief passage over the country. Throughout its path of destruction in Louisiana, more than a million people in total had no electrical power. Widespread heavy infrastructural damage occurred throughout the southeastern portion of the state, as well as extremely heavy flooding in coastal areas. New Orleans' levees survived,^[6] though power line damage was extensive throughout the whole city. There was also substantial plant destruction in the state. The remnants of the storm produced a destructive tornado outbreak and catastrophic flash flooding in the Northeastern United States on September 1. Flooding in New York City prompted the shutdown of much of the transportation system.

As of September 15, a total of 112 deaths have been confirmed in relation to Ida, including 95 in the United States and 20 in Venezuela. In the United States, 33 deaths were in Louisiana, 30 in New Jersey, 18 in New York, 5 in Pennsylvania, 3 in Mississippi, 2 in Alabama, 2 in Maryland, 1 in Virginia, and 1 in Connecticut. The storm has caused 43 indirect deaths, including 20 deaths in Venezuela caused by flooding from Ida's precursor.^[7] A Louisiana man was mauled to death by an alligator after walking through Ida's floodwaters,^[8][9] Two electrical workers died while repairing power grid damage caused by the storm.^[10] while four people died in New Orleans and Jefferson Parish as a result of carbon monoxide poisoning while using generators with inadequate ventilation.^[11][12] After the storm had passed, nearly all of the oil production along the Gulf Coast was shut down. Thousands of emergency crew members were deployed in Louisiana, and hundreds of residents were rescued.^[13] Power outages in the most heavily affected areas were expected to last for up to a month. States of emergency were declared for Louisiana and portions of the Northeast. Several sporting events were also moved, delayed, or cancelled due to the storm.