Stressors
Coastal storms
Key takeaways
- The Northeast U.S. (NEUS) has experienced a strong increase in the frequency and intensity of coastal storms.
Nor’easters have been shifting their tracks northward and increasing in intensity. - The NEUS is especially vulnerable to northward-moving tropical storms that expand in size while retaining high moisture content and strong winds.
- Tropical storms cause significant coastal wind damage and widespread flooding across the NEUS, compounded by rising sea levels.
- Climate projections indicate that coastal storms will likely get stronger, but uncertainty remains regarding the extent and timing of these changes.
The Northeast United States (NEUS) is affected by winter coastal storms each year and occasionally by tropical storms and hurricanes. Coastal habitats and species are vulnerable to storm impacts, particularly to erosion and flooding due to storm surges and heavy precipitation. While climate change is expected to affect the intensity, duration, frequency, and track of coastal storms, understanding the relationship between climate change and coastal storms remains challenging. Climate models are continually improving and increasing our understanding of how coastal storms may change in the future.
Tropical Storms
Tropical storms include tropical depressions (with maximum sustained surface winds less than 39 mph), tropical storms (less than 74 mph), and hurricanes (greater than 74 mph). The strongest tropical storms (hurricanes) have become more intense over recent decades due to warming ocean waters. This trend is likely to continue throughout the 21st century as ocean temperatures continue to warm. There has also been an increase in the number of tropical storms and hurricanes. In the North Atlantic, the number of storms could increase from an average of roughly 6 per year to 8 per year this century.12 However, there is still some uncertainty in these projections. The U.S. could experience slightly fewer tropical storms per year overall by late this century, but a greater number of the strongest hurricanes (category 4 and 5). Rainfall associated with hurricanes could become heavier and more severe as well.
Since 1851, 169 tropical storms and 100 hurricanes have made landfall in the NEUS. Recent extremely large and devastating Hurricanes Irene (August 2011), Sandy (October 2012) and Dorian (August-September 2019) had major impacts on natural resources and human infrastructure in coastal and inland areas. Despite weakening considerably before making landfall in the United States, Hurricane Henri (August 2021) brought very heavy rainfall over the NEUS, causing widespread flooding in many areas, including cities such as New York and Boston. The impacts of these storms are exacerbated by rising sea levels. These events demonstrate that many of the states’ and region’s coastal resources are highly vulnerable to extreme storms and flooding.
Tropical storms are fueled by warm ocean surface waters. As the ocean becomes warmer, not only will hurricanes become stronger, but the source of fuel for hurricanes may expand northward. This will enable hurricanes to persist longer and maintain their strength further north. As a result, tropical storms tracks may shift along the Atlantic coast with a corresponding rise in the number of hurricanes making landfall on northern Atlantic coastal states. In the past, hurricanes generally weakened into tropical depressions by the time they moved into the region; more hurricane-force conditions means there could be greater impacts of extreme storm events on NEUS.
While global climate models are continually improving, the spatial resolution of climate models remains too coarse to adequately capture storms and predict with certainty how tropical storms will change as a result of climate change. Projections of tropical storms are also limited by the complexity of hurricane development and our incomplete understanding of related and interacting climate variables, such as wind shear, vertical temperature gradients in the atmosphere, and warming in the tropical Atlantic Ocean. However, there is high confidence in how climate change will affect variables related to tropical storm development. For instance, ocean temperatures are expected to continue rising, which means tropical storms will likely get stronger overall.
Nor’easters
A class of winter coastal storms known as nor’easters (named for the predominant wind direction experienced in the areas affected) is a major threat to Northeast coastal ecosystems. Nor’easters produce long periods of heavy snow or rain and strong winds, which can lead to high tides, coastal flooding, and beach erosion, as well as large accumulations of snow and rain further inland.
Winter storms, including nor’easters, occur more frequently in the Northeast than tropical storms. Since the 1970s, nor’easters have been shifting their tracks northward and increasing in intensity. The strongest nor’easters are becoming stronger, with both the maximum wind speeds of the most intense (>66th percentile) nor’easters and hourly precipitation rates increasing since 1940 (Chen et al 2025). These changes intensify coastal flooding and erosion risks for cities and shorelines.
Compounded impacts of rising sea levels
Rising sea levels can enhance the impact of storm surges during winter storms (e.g., Nor’easters), hurricanes, and other severe weather events. Higher sea levels mean that storm surges can penetrate further inland, causing more extensive flooding and damage. The rise in sea level is also contributing to an increase in the frequency and duration of minor coastal flooding events (called ‘nuisance’ or ‘sunny day’ flooding) along the U.S. east coast (Sweet et al., 2018; Ezer, 2020). Additionally, storm surges and coastal flooding can have significant impacts on groundwater in coastal areas. Higher sea levels lead to increased coastal erosion as waves reach further inland, wearing down shorelines and threatening coastal infrastructure.
References
Adapted from
Staudinger, M.D., A.V. Karmalkar, K. Terwilliger, K. Burgio, A. Lubeck, H. Higgins, T. Rice, T.L. Morelli, A. D'Amato. 2024. A regional synthesis of climate data to inform the 2025 State Wildlife Action Plans in the Northeast U.S. DOI Northeast Climate Adaptation Science Center Cooperator Report. 406 p. https://doi.org/10.21429/t352-9q86