The 2024 hurricane season is off to a concerning start. Record-breaking sea surface temperatures are changing how and when hurricanes form. Hurricane Beryl broke records for a storm of its kind so early in the hurricane season, killing 64 and knocking out power to millions in Houston. Tropical Storm Debby has caused catastrophic flooding up and down the South Atlantic coast. And, hurricane season is just getting started.

Deep Sky Research analyzed millions of public data points to build a Hurricane Rainfall Model based on the past four decades of climate data to examine these trends. The frequency and severity of extreme hurricane rainfall is climbing. 

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What to Expect from an Unprecedented Hurricane Season

Most deaths caused by hurricanes are a result of the massive volumes of water they drop on coastal areas. The water has a financial impact as well – insurance companies are pulling out of states like Florida because of the flood risk. This is fueling a crisis in home insurance and hurting home values. 

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Finding 1: Frequency of Extreme Hurricane Rainfall has Jumped 300%

Deep Sky Research’s model finds that severe hurricane rainfall that used to occur only once every 100 years will now happen every 25. The most severe hurricane downpours, and the flooding, destruction, and deaths they cause are 300% more likely than they were 40 years ago. See our explanation of “return periods” in our Methodology post.

The probability of smaller storms has doubled – like Hurricane Beryl, which just had such devastating impacts on the Houston area and the Caribbean. The volume of rainfall that fell in one day over the Houston area was previously seen once every 7 years, but it will now happen on average every 3. These are no longer rare events; they will happen with greater frequency and severity. It’s our new normal. 

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Finding 2: Severity of Extreme Hurricane Rainfall has Grown 33% 

Not only has the frequency of extreme hurricane rainfall increased, but the maximum severity is growing as well. Maximum hurricane rainfall has jumped by 33%. The model analyzes 24-hour total precipitation data across the Southeastern US during hurricane season. 

This means that the worst case scenario hurricane today is much more damaging than it used to be – the ceiling has been lifted. Hurricanes have caused the most damage of any weather disasters over the past forty years in the US: over $1.3 trillion, killing thousands of people. What does it mean if the worst hurricanes get even more intense? 

Of course, this isn’t an overnight change. Extreme hurricanes like Katrina and Harvey were more severe as a result of this trend. But the model predicts this trend is not slowing down and even more damaging hurricanes are coming, both this year and into the future.

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Finding 3: Hurricanes could cost more than $450B in the next 5 years (a 50% increase)

Deep Sky Research projects losses of more than $450B USD in the next 5 years across Gulf and South Atlantic coast states due to hurricanes. Florida is expected to have the greatest losses, with Texas a close second. The projection is based on a proprietary Deep Sky machine learning model which incorporates the worsening precipitation trends outlined above, historical hurricane damages over the past 40 years, observed changes in the climate like rising sea surface temperatures, as well as increasing population and investment in hurricane-vulnerable areas. The data used in Deep Sky’s analysis is publicly available from the Copernicus Climate Data Store, NOAA, and the US Census. The model has built-in limitations and significant uncertainty laid out in more detail in the Technical Appendix.

This figure is a 50% increase over the last 5 years, which includes 2022, the third-costliest Atlantic hurricane season on record. Deaths will also climb due both to the immediate impacts of the storms, and from second order effects like power outages (discussed below). 

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Finding 4: Gulf Coast States Face Greatest Rainfall Increases

Hurricane rainfall severity is increasing more in some places than others. States along the Gulf Coast including Texas, Louisiana, and Mississippi should expect the greatest increases while those on the Atlantic coast such as North Carolina and South Carolina will see smaller increases. Georgia has actually seen a slight decrease over that same time period.

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Finding 5: Flash flooding will now hit South Atlantic counties every year 

Torrential rainfall combined with storm surges – the rapid water level rise resulting from tropical storms – cause flash flooding. Storm surge is worsening because hurricanes are getting stronger but also because sea levels are rising. This means that when a storm surge occurs, flooding is more severe. 

It’s no longer the rare storm that causes severe flooding. Deep Sky Research found it’s now expected to happen up and down the South Atlantic coast every year. 

The map below shows the total flooded area and median flood depth that will occur on average every year for each county along the South Atlantic coast. The equivalent data is not yet available for the Gulf Coast.

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Flooding is most destructive in densely populated areas. The Miami metropolitan area has over 6 million people. Each of its three counties is extremely vulnerable to flash flooding caused by hurricanes. 

One storm per year is now expected, on average, to reach the depth shown in the modeled visualization below. The image shows 2.5 feet of flooding in Miami Beach. Local governments are working hard to protect citizens from damages but only so much is possible in the face of the increasing severity and frequency of flooding. 

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Deep Sky Research worked with Climate Central FloodVision to produce the image in order to illustrate the risks of future storms.  

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Floridians statewide have much larger flooding vulnerability than their neighbors in other Southeastern states

And, Floridians are feeling the effects.

Deep Sky conducted a survey of Americans and found that 24% of respondents have experienced property damage from extreme weather as a result of climate change. Floridians were more than twice as likely to have experienced damage than the average respondent.  

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Finding 6: Houston is Most Vulnerable to Hurricane-Caused Power Outages

Hurricane Beryl left hundreds of thousands in the Houston area without power for over a week, and over 2 million lost power in total. The damage and loss of life from hurricanes like Beryl are aggravated by the power outages they cause. Some people were killed not by the hurricane itself, but by the heat exposure following the loss of power and lack of air conditioning.

Beryl highlights a growing risk for Americans living near the Gulf and Atlantic coasts. Data from the past decade shows where the grid is most vulnerable to hurricane-caused power outages. The map below shows each county’s Hurricane Outage Risk.

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This table shows the ten counties with the greatest hurricane-caused power outage vulnerability. For 9 out of 10, that vulnerability is increasing. As Beryl made all too clear, the Houston area is particularly vulnerable. This is due in part to its likelihood of being in the path of severe storms, and in part because of well-documented problems with the Texas power grid. Most Houston residents have considered leaving the area and more than half of those cite extreme weather as a reason.

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Table 1: Counties with Greatest Hurricane Outage Vulnerability

Hurricane-caused power outages are particularly dangerous because they tend to hit during the hottest time of the year, in places with very high temperatures. Prolonged exposure to high temperatures without air conditioning can cause a wide range of health problems and even death.

Power outages also impact hospitals’ ability to save patients, as Dr. Storr, Consultant Emergency Medicine Physician at Rand Memorial Hospital on the island of Grand Bahama, experienced firsthand following Hurricane Dorian in the Bahamas in 2019. 

“Power outages created challenges with poor ventilation from air conditioning units not working, requiring windows and doors to be opened,” Dr. Storr explained. “These outages made providing reliable medical procedures such as renal dialysis and other treatments difficult for the healthcare system. Persons also presented weeks later with respiratory complaints due to mold growth from flooding. Later, some survivors developed mental health illnesses such as anxiety, depression, and PTSD as they grappled with the loss of loved ones and property. Medical responders also experienced burnout from working in prolonged emergency conditions with limited resources and staffing shortages.”

Conclusion

Many of the impacts of climate change are slow-moving, but some will be devastating in their rapid escalation. We will see the impacts of worsening hurricanes not in the next 50 years, but in the next 5. This will mean billions of dollars in damages, hundreds of thousands of homes destroyed, and many lives lost. 

Imagining hurricanes worse than Katrina and Harvey is not easy. But rather than waiting for last minute evacuations, we should seriously analyze the risks in front of us so that we can be most prepared. 

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Methodology

The fundamentals of Deep Sky’s research are laid out in this post on how we model the climate. 

This report analyzed 40 years of hurricane data from 1983-2024 across the Southeastern United States. Data used in this report includes ECMWF Reanalysis v5 (ERA5) precipitation and sea surface temperature data downloaded from Copernicus Climate Data Store, historical damages data from NOAA, projections of coastal flood hazard from USGS, historical power outage data from EAGLE-I Power Outage Data as well as Department of Energy OE-417 reports, and data on changing capital stock in hurricane-vulnerable areas from the US Census. As mentioned above, Deep Sky Research worked with Climate Central FloodVision in order to visualize flood hazard in Miami Beach. 

The report makes use of extreme value statistics for precipitation trend modeling, and machine learning for analysis of hurricane damages. A Technical Appendix is available upon request.