Costliest tropical cyclone

The costliest cyclones in terms of property damage (non-inflation-adjusted) are Hurricane Katrina (2005) and Hurricane Harvey (2017).

Hurricane Katrina made landfall as a strong Category 3 tropical cyclone on 29 August 2005 with winds of around 200 km/h (125 mph). The city of New Orleans and surrounding areas of Mississippi, Louisiana and Alabama bore the brunt of the hurricane-force winds and the highest storm surges, though Katrina left a trail of destruction that stretched from Louisiana to Ohio. Flood defenses failed in many places, most notably in New Orleans, amplifying the destructive effects of the hurricane and causing as many as 1,800 deaths. In its report on the hurricane, the NOAA (National Oceanographic and Atmospheric Administration) states that the insured losses as a result of Katrina amounted to $66.9 billion, and that the total cost of the damage was around $108 billion. The NOAA later revised this figure up slightly, to $125 billion (with a broad confidence interval).

Hurricane Harvey made landfall as a Category 4 tropical cyclone on 26 August 2017 near Rockport, Texas. At the time of landfall it had wind speeds of around 115 knots (212 km/h; 132 mph) and a minimum central pressure of 937 millibars. After making landfall it drifted slowly through central Texas, dumping a catastrophic 60.58 inches (1.53 metres; 5 ft) of rain in the area around the city of Houston and causing widespread flooding. In its official report on the event, the NOAA estimated that Hurricane Harvey had caused around $125 billion of damage (with a 90% confidence interval ranging from $90 to $160 billion).

Katrina remains the costliest tropical cyclone when the cost of the damages is adjusted for inflation, though some methodologies for this produce differing results.

The 2005 Atlantic hurricane season was the most severe on record. The NOAA recorded 15 hurricanes, of which seven were Category 3 or above, and dozens of storms and tropical depressions. In addition to Katrina, severe damage was done by hurricanes Dennis, Rita and Wilma, which caused $2 billion, $10 billion and $12 billion in damage respectively.