Fact check: Several hurricanes, including Ida, have hit Louisiana on Aug. 29

Bayliss Wagner, USA TODAY
·6 min read

The claim: Dates of Hurricanes Katrina, Gustav, Isaac and Harvey are all Aug. 29

Hurricane Katrina roared into Louisiana as a Category 3 storm on Aug. 29, 2005, soon to become the deadliest hurricane so far in the 21st century.

Exactly sixteen years later to the day, Hurricane Ida, a Category 4 storm with 150-mph winds, made landfall in the state – and a viral claim says that's not the only time the 29th day of August has brought disaster.

Shared by thousands of users across several Facebook posts, the claim lists the dates of historic Gulf Coast Hurricanes Katrina, Gustav, Isaac and Harvey as Aug. 29 in 2005, 2008, 2012 and 2017, respectively.

Other posts list Ida next to the date it made its first landfall in the U.S. on Sunday, Aug. 29.

But is Aug. 29 the Gulf Coast's equivalent of Friday the 13th? Not exactly.

All of the hurricanes listed were active on the 29th, but Aug. 29 doesn't mark the same event for each. Some made landfall in the U.S. around that date, but others were still offshore.

Major hurricanes are statistically most likely to occur in late August, September and early October as a result of favorable weather conditions, including low wind shear, high atmospheric moisture and warmer ocean and air temperatures.

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USA TODAY reached out to several users who shared the claim for comment.

Hurricanes Gustav, Harvey didn't hit on Aug. 29

Users who post the meme suggest a parallel between the four historic storms and Hurricane Ida.

But only two of the historic storms listed in the meme, Katrina and Isaac, made landfall in the U.S. on the 29th day of August. Unlike Ida, none of the hurricanes listed in the post first hit the U.S. on Aug. 29.

According to the National Hurricane Center's post-storm report, Hurricane Katrina passed over southern Florida as a Category 1 storm on Aug. 25, 2005. It then gained strength over the Gulf of Mexico and slammed into Louisiana and Mississippi as a Category 3 on Aug. 29. The storm caused extensive damage in a short time, losing its hurricane-speed winds late that night.

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Hurricane Isaac hit Louisiana on Aug. 29, 2008, like Ida. However, that also wasn't its first U.S. landfall. The tropical storm had hit the southeastern Louisiana coastline with 80 mph winds on Aug. 28, then edged back over the Gulf's waters before making a second landfall in Louisiana on Aug. 29, according to the National Hurricane Center.

Hurricane Gustav, formed on Aug. 25, 2008, but it didn't hit the U.S. until Sept. 1, when it landed in Lousiana as a Category 2 storm. It made its first landfall in Haiti on Aug. 26, where it caused severe damage and killed dozens as it passed over Cuba, then moved up to the Gulf Coast, National Hurricane Center records say.

Finally, Hurricane Harvey hit southern Texas at Category 4 strength on Aug. 25, 2017, rather than four days later. By the time Harvey eventually made a second landfall in Louisiana on Aug. 30, it had weakened to a tropical storm, the National Hurricane Center reports.

Harvey devastated coastal Texas communities and took Katrina's place as the costliest storm to ever hit the U.S. mainland, USA TODAY reported in 2017.

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Though not all of these storms made major landfalls on Aug. 29 of their respective years, it's clear that late August is a dangerous time for hurricane activity on the Gulf Coast. At least nine major hurricanes have hit the coastal U.S. in the last week of August, Louisiana CBS affiliate KALB reported.

However, the statistical peak day of the hurricane season for the Atlantic basin as a whole is a bit later. Tropical cyclones are most likely to be active on Sept. 10, according to the National Oceanic and Atmospheric Administration.

Late August is hurricane season

That Katrina and Isaac both hit Louisiana on Aug. 29 may be enough to evoke superstition for some, but there's a scientific explanation for why so many of the most devastating tropical storms occur around this time of year.

Statistically, the most dangerous hurricanes are most likely to hit between mid-August and mid-October.

"A whopping 96 percent of the major – category 3, 4 and 5 – hurricane days" occur during those eight weeks, NOAA says on its website.

The reason has to do with temperature, wind and moisture conditions at that time.

This GOES-16 East GeoColor satellite image taken Thursday, Aug. 26, 2021, at 10:20 p.m. EDT, and provided by NOAA, shows Tropical Storm Ida in the Caribbean Sea. Tropical Storm Ida formed in the Caribbean on Thursday and forecasters said its track was aimed at the U.S. Gulf Coast, prompting Louisiana's governor to declare a state of emergency and forecasters to announce a hurricane watch for New Orleans. (NOAA via AP)

According to NOAA, most hurricanes originate from tropical waves that roll off of Africa's coast regularly throughout the hurricane season, from June 1 to November 30.

Many of these waves dissipate as a result of wind shear, which "tears disturbances apart before they can begin." But wind shear is at a minimum for stretches of that season.

In addition, the period between mid-August to mid-October sees warmer air temperatures, more atmospheric moisture and the highest ocean temperatures in the deep tropics, where hurricanes form.

Combined, these conditions create what could be called the perfect storm for major hurricane formation.

Our rating: Missing Context

Based on our research, we rate MISSING CONTEXT the claim that the dates of Hurricanes Katrina, Gustav, Isaac and Harvey are all Aug. 29. The post doesn't specify the significance of Aug. 29, but it suggests a key event aligned for all of the hurricanes on that date. Hurricanes Katrina and Isaac both made landfall in Louisiana on the 29th day of August, but had first hit the U.S. on previous dates. In contrast, Hurricanes Gustav and Harvey were both offshore on Aug. 29.

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This article originally appeared on USA TODAY: Fact check: Ida one of several historic hurricanes to hit Louisiana on Aug. 29