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The Southeast region of the United States boasts tremendous diversity across the natural environment and the people who live there. Bounded by the Gulf of Mexico and Atlantic Ocean, much of the region is a vast coastal plain lying below piedmont, elevated plateaus, and highlands. The region is home to important mountain ranges, including the Appalachians, Ozarks, and Alleghenies, as well as major rivers including the Mississippi, Ohio, Tennessee, and Savannah.

The Southeast has a rich cultural history tied to these landscapes, and the region continues to diversify and grow in population, particularly in cities and in the coastal zone. Both rural communities and high-growth urban areas contain pockets of severe poverty and deep-rooted inequality. The region is also home to a variety of ecosystems containing unique animal and plant communities with globally recognized biodiversity value, from coral reefs and coastal marshes to forests, swamps, and rolling grasslands in the interior.

Observations over the past 100 years have shown uneven warming across the Southeast, with an upward trend recently becoming apparent. The decade from 2010–2020 was the warmest on record for the region, and the Southeast is now experiencing a higher percentage of intensifying heat waves than any other part of the country (see Heat, Health, and Livelihoods in Rural Impacts; see Temperature, Humidity, and Heat Waves in Urban Impacts).

The Southeast generally receives a lot of rain, and total rainfall is increasing across most of the region. The number of heavy rain events has increased slightly in most areas, and this trend has accelerated in the most recent decades.

Across the Southeast, the number of days per year with heavy precipitation (shown by decade on the left) has generally increased since the 1900s. On the right, dots show individual station trends toward more (red) or less (blue) heavy precipitation from 1950 to 2016. Fourth National Climate Assessment, Figure 19.3.

Despite the increase in heavy rain events, the Southeast also experiences drought. Especially during strong La Niña years, the southern portion of the United States receives lower than average rainfall. In the early 2010s, much of the south received record low rainfall, which resulted in significant drought.

Projections of future conditions from climate models suggest that temperature and rainfall will continue to change in the Southeast. Temperature will increase, resulting in more frequent and dangerous heatwaves and potentially leading to more severe droughts. Extreme rainfall events are generally likely to become more frequent and intense. Projections vary based on greenhouse gas emissions, with high greenhouse gas emissions over the next several decades resulting in bigger changes to temperature and rainfall. For example, if greenhouse gases continue increasing, summer temperatures above 95°F are projected to become very common by the end of this century. For additional information, see the Fourth National Climate Assessment, Chapter 19; Southeast.

Non-climate stressors such as persistent poverty can exacerbate climate-related hazards. For instance, health impacts from extreme heat and higher humidity can be magnified in housing without adequate air conditioning, exposing those without access to cooling to higher rates of heat-related illness. These non-climate stressors are often associated with economic factors such as lack of access to jobs and healthcare or demographic factors such as gender, race, and disability.

An example of a climate-related stressor that could impact agricultural productivity in the Southeast comes from dryland (rain-dependent) agriculture. This sector is particularly sensitive to drought due to the method of farming itself; more frequent or intense droughts could decrease yields or necessitate shifts in crop selection. Climate change will also affect the vulnerability and risk to animals, plants, and habitats across the region.