Billion-Dollar Weather and Climate Disasters: Climatology
The charts below capture the total duration of each billion-dollar disaster. Therefore, events that span multiple months are counted in each of the months in which they occur.
Climatology of Weather and Climate Disasters
The charts above show the 40-year history of U.S. 'compound extremes' (e.g., billion dollar disaster events that occur at the same time or in sequence). As noted in National Climate Assessment (2017) "the physical and socioeconomic impacts of compound extreme events (such as simultaneous heat and drought, wildfires associated with hot and dry conditions, or flooding associated with high precipitation on top of snow or waterlogged ground) can be greater than the sum of the parts."
The 40-year climatology of U.S. billion-dollar disasters offers a view of risk from extreme events, which are often seasonal in nature. For example, during the spring months (March-May) severe storms including tornadoes, hail and high winds often occur in many Central and Southeast states. During the spring months there is also potential for major river flooding (i.e., deep blue events in chart above). U.S. springtime flooding from snowmelt and/or heavy rainfall is a persistent hazard that affects many towns and agriculture regions within the Missouri and Mississippi River basins, among others.
During the fall season, Gulf and Atlantic coast states must be vigilant about hurricane season particularly during August and September (i.e., yellow events in chart above). Hurricanes are the most destructive and costly of these events totaling damage losses near $1 trillion since 1980. For example, in 2016-2018, the U.S. was impacted by 6 separate billion-dollar hurricanes (i.e., Matthew, Harvey, Irma, Maria, Florence, Michael) with an inflation-adjusted loss total of $339.7 billion and 3,318 fatalities. As a comparison, the U.S. also experienced a series of active hurricane seasons from 2003-2005 where 9 separate billion-dollar hurricanes (e.g., Charley, Ivan, Katrina, Rita, Wilma, etc.) made landfall, with an inflation-adjusted loss total of $308.1 billion and 2,225 fatalities.
Also, the peak of the Western U.S. wildfire season occurs during the fall months of September, October and November (i.e., orange events in chart above). California, Oregon and Washington are often states that face wildfire risk and related poor air quality for weeks to months. Western wildfire risk is also becoming more hazardous, as 17 of the 20 largest California wildfires by acreage and 18 of the 20 most destructive wildfires by # of buildings destroyed have occurred since the year 2000. In three of the last four years (2017, 2018 and 2020) California has experienced historically large and costly wildfires with losses well exceeding $50.0 billion. 2020 was another record-breaking U.S. wildfire season that burned more than 10.25 million acres.
In total, each region of the U.S. faces a unique combination of recurring hazards, as billion-dollar disaster events have affected every state since 1980. The two charts above highlight how the frequency of billion-dollar disasters differs across both time and space. The combined historical risk of U.S. severe storms and river flooding events places the spring and summer seasons in the high-risk category for simultaneous extreme weather and climate events.