Weather Volatility 101

Weather volatility refers to the frequency, intensity, and variability of weather events such as temperature swings, extreme heat, heavy precipitation events, and storms. While the effects of climate change on average temperatures and rainfall are now well-established, understanding how climate change affects weather extremes is more challenging.

Highly variable weather is not just a meteorological concern but a profound economic and social issue. One study from 2021 highlighted how the increased volatility that contributes to more frequent and severe storm events disrupts agriculture, infrastructure, and overall economic stability across multiple countries. Further in-depth research on the linkage between climate and economic performance reveals that the stakes of inaction are high, with the potential to undo decades of economic development and worsen global inequalities. A recent study estimated that temperature variability raises the average social cost of carbon—an estimate of the economic damages resulting from emission of an additional ton of carbon dioxide—by 6.5 percent to $307 per ton.

This explainer summarizes trends in extreme heat, precipitation, and weather disasters in the United States as well as findings in literature on the impacts of those events.

As climate change intensifies, the United States has seen a marked increase in the frequency and intensity of annual heatwaves. Examining heatwave data available on the Resources for the Future (RFF) Weather Variability Explorer (WeaVE) reveals how heatwave incidence has skyrocketed since the 1980s, and where the increasing frequency is geographically concentrated. This database defines a heatwave as a stretch of at least two successive days during which the lowest daily temperature surpasses the 85th percentile of historical temperatures recorded for July and August in that specific area.

The maps below in Figure 1 show the five-year average annual heatwave count in each US county in the periods of 1981–1986 and 2016–2020. The number of heatwaves nationwide has doubled from an average of 13.22 in 1981–1986 to 27.30 in 2016–2020, an increase of 106 percent over 40 years. Visualizing the change illustrates how the counties with the highest number of heatwaves have shifted south from the central United States and Midwest to the Gulf Coast states.

Within the wider national trends, the data reveals that certain geographic areas stand out. The top three counties with the highest increase in heatwave count—Hardee, Highlands, and Osceola, all located in Florida—exemplify this trend. Hardee County, for instance, experienced 57 more heatwaves per year, on average, during the 2016–2020 period compared to the 1981–1986 period, an increase from 10 to 67. Similarly, Highlands and Osceola Counties also saw substantial increases, with both having 51 more heatwaves in the later period. Further information and a more detailed version of this map can be found on the RFF Data Commons, where the data show how the length of heatwaves has also increased along with the frequency, especially in southwestern states.

The rise in temperature extremes is further exacerbated in cities by the urban heat island effect, where human-caused environments—characterized by concrete, asphalt, and other heat-absorbing materials—significantly elevate temperatures compared to surrounding rural areas. The retention of excess heat by the built environment can raise nighttime temperatures by 2° to 5°F, with densely packed urban centers experiencing increases of 15° to 20°F.

These heat islands create conditions that intensify heatwaves, making urban areas particularly vulnerable to the adverse impacts of elevated temperatures. The disparity in temperature within a city varies, with the most built-up regions experiencing the highest increases, highlighting the importance of urban planning and green space in mitigating heat effects. This is a key environmental justice consideration, as studies show people of color and those of lower socioeconomic status have access to smaller areas of green space of lower quality and safety than wealthier neighborhoods.

Adaptation to extreme heat, which includes investments in urban green space, changes in building materials, creation of community cooling centers, and a variety of approaches to reduce human vulnerability, is crucial as research shows high temperatures are responsible for more fatalities than flooding, hurricanes, and tornadoes in the United States combined.

Climate change impacts on precipitation vary by location, but globally, average annual precipitation is on the rise. A 2021 paper found that as surface air temperatures rise, the hydrological cycle intensifies, leading to a 1 to 3 percent increase in global mean precipitation for every 1.8°F of warming.

Precipitation extremes can be measured in different ways. One measure is the share of annual rainfall that occurs over a limited number of days of the year. Using the RFF WeaVE, Figure 2 plots, for the years 1980–2020, each state’s percentage of annual rainfall that occurs on days with extreme precipitation, defined as the highest 10th percentile. If precipitation occurs uniformly over the year—i.e., every day gets exactly the same amount of rain—then the extreme one-day precipitation statistic would be 10 percent. However, precipitation does not occur uniformly, as Figure 2 shows, and states vary significantly in the extent to which they receive rainfall in extreme events or more evenly throughout the year.

California, Arizona, and Texas have the highest extreme one-day precipitation totals in most years, and West Virginia, Vermont, and New York have the lowest. In 2016, for example, California received 30.97 percent of its rainfall for the year on extreme rainfall days. By contrast, West Virginia received only 15.72 percent on extreme days. States with an arid climate receive less rainfall overall than temperate states. Consequently, the days of extreme one-day precipitation stand out as a greater percentage of the annual total for states where long dry seasons are typical. The analysis highlights that like heatwaves and other consequences of climate change, the effects of changing rainfall patterns will not be felt equally in geographically diverse countries like the United States, thus regionally targeted adaptation efforts are needed.

The black line in Figure 2 shows the national average, which is around 20 percent but has trended slightly upward over the period of the data. Closer inspection of the data reveals that extreme precipitation in the U.S. overall has increased by about 5.1 percent annually, on average, over the last 40 years.

Extreme precipitation over a short period can trigger flash floods, which are floods that occur when a high volume of water moves through a riverbed or over roads and other surfaces in a short period of time. The National Weather Service reports that flash floods are the number one storm-related cause of death in the United States, driven by drowning victims who fatally underestimate the power of uncontrolled water while trying to cross flooded areas. A recent study concluded that floods in the continental US will become “flashier” by the end of the century because of climate change. Using a combination of weather and hydrological modeling, the authors calculated that US floods will be 7.9 percent more spontaneous—that is, they will initiate more quickly, accompanied by heightened peak runoff, and thus reducing the window for early warnings to mitigate avoidable casualties. The Probable Maximum Precipitation Measure, which refers to the maximum possible precipitation depth at a specific location for a designated duration, is used in the design of dams, bridges, stormwater infrastructure, and other investments. Going forward, this measure will need to account for climate change to ensure infrastructure investments can help build resilience to weather extremes.

The causes of all types of floods and flood damages are multi-faceted, but one study from 2021 established a clear link between heightened monthly precipitation and an increase in flood damages, with a 1-standard deviation rise in precipitation anomalies tripling flood-related economic losses. This relationship reveals that even slight shifts in precipitation patterns due to climate change can have significant economic impacts. The authors calculated that precipitation changes contributed 36 percent ($73 billion, about $220 per person in the United States) of the 1988–2017 cumulative US flood damages.

Rainfall variability can affect economic outputs. A 2022 paper finds that while initially, an increase in annual rainfall may boost a country’s economic growth, overly high or erratic rainfall figures correlate with economic downturns. This is particularly true for economies that are not accustomed to such variations, emphasizing the need for local adaptive strategies in the face of increasingly unpredictable weather. The economic toll of increased rainy days and extreme rainfall events is particularly stark in high-income regions, affecting sectors like manufacturing and services the most.

The National Oceanic and Atmospheric Administration (NOAA) tracks the number of major annual weather-related disasters in the United States and their associated costs. This includes droughts, flooding, wildfires, hurricanes, blizzards, and other severe storms. Figure 3 illustrates the number of billion-dollar disasters each year since 1980. The number of weather disasters has doubled from an average of less than five in the 1980s to more than ten after 2008 before doubling again in the 2020s. This increase in severe weather events has brought with it higher economic burdens in disaster damage and recovery costs.

Figure 4 shows the total inflation-adjusted cost of disasters in 2024 dollars for each year from 1980 through 2023. The spikes in 2005 and 2017, respectively, correspond to the years of Hurricane Katrina (and Rita) and Hurricanes Harvey, Irma, and Maria (in what was the most destructive hurricane season in history to date with estimated losses nearing $400 billion, about $1,200 per person in the United States). These costs are not borne evenly, as certain regions are more vulnerable to different types of weather disasters. Although southwestern states are more prone to droughts, the Gulf Coast states are most vulnerable to hurricanes, which are the costliest types of disasters.

While hurricanes and other types of disasters impose significant losses in the form of physical damages to property and public infrastructure, building content losses, crop damage, and costs that arise from business disruptions, studies have found that disasters have ambiguous effects on local economies. The initial disruption to some businesses can reduce sales, employment, and wages and have a compounding negative impact throughout the local economy. If damage is substantial, some establishments may shut down or relocate.

On the other hand, construction for rebuilding generally provides a local economic boost, and if disasters spur residents to relocate away from affected areas, local labor supply may fall and put upward pressure on local wages. Effects on local household income are therefore ambiguous, with insurance payouts, disaster aid, and other government assistance often offsetting negative shocks. A recent study looking across all types of disasters in the United States and using county-level data over a 30-year period found no long-run evidence of negative economic outcomes. However, studies of especially devastating hurricanes (Katrina and Sandy) show negative effects on business survival in local communities most affected by the hurricanes.

Policies to address the impacts of climate change need to recognize changes in weather extremes and volatility and not just shifts in temperature and precipitation means. Land use and infrastructure investments need to plan for “tail risks”—low probability, high-impact events. A better understanding of the role of green infrastructure (bioswales, rain gardens, permeable pavements, and a range of other nature-based solutions) for managing extremes is also needed. Finally, a better understanding of how to adapt to both slow-moving changes in means—e.g., higher average temperatures expected over the next several decades—as well as increases in weather extremes is needed.

Diversifying economically and enhancing climate research will further equip communities to handle and recover from weather-induced disruptions. Policies aimed at mitigating climate change effects are crucial, alongside education to elevate public understanding and preparedness. Future research should refine economic impact models of climate events and explore localized socioeconomic consequences to inform targeted adaptation strategies.