Storm Watch: Mapping Extreme Weather Events in the United States

Margaret A. Walls and Yanjun (Penny) Liao

Certain regions in the United States are especially susceptible to extreme weather events, which are increasing in frequency and intensity due to climate change.

Special Series: Weather Volatility in the United States

Climate change is increasing the frequency and intensity of extreme weather events in the United States. In this series of blog posts, experts examine trends in extreme weather, impacts on communities, and policies that potentially could mitigate damage from extreme weather events.

In our first blog post on weather volatility and climate change, we describe trends in extreme weather events in the United States from 1995 to 2022 and how different types of weather events (such as floods, hurricanes, heat waves, and wildfires) cause different levels of damage. The source of our data is the Storm Events Database from the National Weather Service, which is operated by the National Oceanic and Atmospheric Administration. In that blog post, we also describe our processing and aggregation of these data and our annual county-level data set of damage and deaths from extreme weather events. In this follow-up blog post, we analyze where the weather events tend to occur and dig deeper into the data to identify specific counties that have experienced significant impacts from extreme weather.

That the geographic distribution of impacts from extreme weather varies greatly will come as no surprise. A person living in Louisiana or Florida has a much greater probability of experiencing a hurricane than someone who lives in an inland state, or even in a state along other parts of the US coastline. Wildfires are more a fact of life for people in California than in, say, Nebraska. Tornadoes are more common for Midwesterners than for residents of other parts of the country. In this blog post, we explore these patterns in more detail.

Figure 1 shows total property damage caused by extreme weather events over the 28-year period from 1995 through 2022 for each county in the United States (2022$ adjusted for inflation). The lighter the color, the smaller the economic damage. Many counties in the United States experienced relatively little damage from storm events over the period 1995 to 2022. The relatively small amount of damage doesn’t mean that these counties don’t experience storms, but rather that the damage was smaller there than in other locations. Counties in black and purple experienced the greatest damage, and these counties are concentrated along the Gulf Coast; primarily in Florida, Louisiana, and Texas. Other counties that experienced high amounts of damage are in Arizona, Colorado, New Jersey, New York, and Southern California, and here and there throughout the United States.

Figure 1. Total Property Damage by County, 1995–2022

Notes: The colors in the legend represent percentiles of the distribution of property damage as follows: 0–50th percentile = yellow; 50th–75th percentile = light orange; 75th–80th percentile = orange; 80th–85th percentile = red; 85th–90th percentile = light purple; 90th–95th percentile = purple; and 95th–100th percentile = black.

Property damage from extreme events across all counties in the United States averaged $109.7 million for this 28-year period, or $3.9 million per year per county (2022$). (For context, the average value of all residential properties in a county in the United States in 2020 combined was about $11 billion.) However, the variance in damage across counties is high. Counties in the top 10th percentile experienced $914.7 million of damage on average, while counties in the bottom 10th percentile experienced only $430,000 of damage.

Two factors explain the spatial patterns in the map. The first is the frequency and severity of storm events. In our previous blog post, we showed that hurricanes, though occurring infrequently, lead to the most severe damage of all types of extreme weather events, so regions of the country that are prone to hurricanes—namely, counties along the Gulf Coast—have experienced high levels of damage.

The second factor is the amount of development and the value of the assets at risk. Counties with large populations also experienced high levels of damage from extreme events. For example, Wayne County in Michigan (which is home to Detroit) and Davidson County in Tennessee (which includes Nashville) both are far away from the coast but have relatively large populations and have experienced high levels of damage from storm events.

Figure 2 provides a sense of the importance of the events themselves by dividing property damage per year by the population in each county, revealing damages per capita.

Figure 2. Per Capita Property Damage by County, 1995–2022

Counties along the Gulf Coast still show high levels of damage, even on a per capita basis. But counties in some coastal states that experienced high levels of total damage, such as California, New Jersey, and New York, are lower in the distribution of per capita damage. On the other hand, counties in several Midwestern states saw higher levels of per capita damage than total property damage.

For example, some counties in North Dakota rank in the top 48th percentile in total damage on average but rise to the top 17th percentile on a per capita basis. Iowa, Kansas, and Nebraska have similar patterns. In these states, the financial and social consequences of disasters can be quite high for individuals, even though the total damage from extreme weather events do not stand out nationally. Across all counties, the average amount of property damage per capita from 1995 to 2022 was $1,748, but counties in the top 10th percentile experienced average damage of $11,515 per capita.

Table 1 shows the 15 counties in the United States that experienced the greatest property damage from extreme weather events from 1995 to 2022. These 15 counties account for 35.3 percent of the property damage from extreme events but are home to only 4.3 percent of the US population. These somewhat stunning statistics highlight the geographic concentration of the impacts of extreme weather events in the United States: some areas are much more exposed to risk than others.

Table 1. Fifteen US Counties with Highest Property Damage from Extreme Weather Events, 1995–2022

We’ve noted a few key findings from the data presented in Table 1.

Several of the counties with high total damage have very high populations; namely, Harris and Dallas Counties in Texas and Palm Beach County in Florida. The arithmetic here moves them lower on the list in terms of damage per capita.

In contrast, two Louisiana parishes (the equivalent of counties)—St. Bernard and Plaquemines—have low populations and thus very high damage per capita. The average damage in Plaquemines of $183,675 per capita is 50 times greater than the damage per capita in Harris County, Texas, which tops the list for total damage.

Although we showed in our previous blog post that wildfires cause less total damage than hurricanes and floods, devastating wildfires in Butte and Shasta Counties in California placed those two counties in the top 15 in terms of total damage. The Camp Fire struck the town of Paradise in Butte County in 2018, and the Carr and Camp Fires hit Shasta County in the same year. The Camp Fire was the most destructive wildfire in US history, according to the Storm Events Database via the National Weather Service; the fire caused $16.4 billion in damage. (Most of the damage was in Butte County, but Shasta County and Tehama County also experienced damage from the Camp Fire.)

A single event accounts for the lion’s share of the damage in most of the counties in the top 15 (much like in the case of the Camp Fire and Carr Fire). In the two New Jersey counties in the top 15, Monmouth County and Ocean County, Hurricane Sandy (which occurred in 2012) accounts for 99.2 percent of the total damage from 1995 to 2022 in those counties. Single events loom large even in counties that experienced multiple events; for example, Hurricane Katrina for the parishes in Louisiana that are in the top 15, and Hurricane Ian for Palm Beach County, Florida (Figure 3).

Figure 3. Distribution of Property Damage for the 15 Counties that Experienced the Most Property Damage, 1995–2022

Notes: The counties are listed from top to bottom according to the total amount of property damage they experienced from 1995 to 2022. Harris County, Texas, experienced the most damage, and Lafourche Parish, Louisiana, experienced the least damage.

Some Regions Are at Higher Risk Than Others, but No Region Is Immune

Property damage from extreme weather events in the United States varies significantly across space and time. Some counties are at much higher risk than others. However, the data reveal that, while regions such as the Gulf Coast are especially prone to weather extremes, a single catastrophic event can cause enormous harm and occur almost anywhere. The areas hit by Hurricane Sandy in 2012 and by the Camp Fire in 2018 are prime examples. A lesson from these findings is that, when communities are preparing for weather extremes, they cannot necessarily look to history as a guide. Catastrophic events can occur unexpectedly and cause significant harm. As climate change makes weather more volatile, communities need to prepare for the worst.

In our final blog post in this series about extreme weather, we’ll offer observations about how communities can adapt to become more resilient against extreme weather events. Stay tuned.

Our data and detailed documentation of our related methodology are available in the Harvard Dataverse, a free and public data repository where researchers from various disciplines share, archive, cite, access, and explore research data.

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