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Climate Impact Spotlight: The South Hudson Region

Bear Mountain Bridge stretches across the Hudson River. Mountains can be seen on the horizon. Fall foliage can be seen in the foreground. A barge in the water approaches the bridge.
The Bear Mountain Bridge, linking Orange and Westchester Counties.
Map of South Hudson Region highlighted in blue

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Printable Region Fact Sheet

Get to Know the South Hudson Region

For the purposes of the New York State Climate Impacts Assessment, the South Hudson region includes Dutchess, Orange, Putnam, Rockland, and Westchester counties. The region is a mix of urban, suburban, and rural areas. It contains coastal areas along Long Island Sound in Westchester County and the tidal portion of the Hudson River. Yonkers, the fourth largest city in the state as of the 2020 Census, is in the South Hudson region, as well as many other cities and smaller cities, towns, and villages. Residents in the region are served by Metro-North’s commuter rail lines to and from Grand Central Terminal in New York City. The Hudson line runs up the east side of the Hudson River to Poughkeepsie; the Harlem line runs through Westchester, Putnam, and Dutchess counties; and the New Haven line serves communities along Long Island Sound. Commuter lines west of the Hudson that are operated by New Jersey Transit under a contract with Metro-North. The scenic Hudson River valley is a popular tourist destination and a spot for outdoor recreation for local residents and those traveling from nearby New York City. The region contains many historic estates and other sites and is home to landmarks such as Bear Mountain and the U.S. Military Academy in West Point.

People walk along a pedestrian walkway, formerly a bridge, across the Hudson river.
The Walkway Over the Hudson in Poughkeepsie is a former railway bridge converted into a pedestrian walkway and part of the Empire State Trail bike route.

The South Hudson Region’s Changing Climate

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Average temperatures are projected to increase in all seasons across all regions of New York State. Averaged over the entire year, temperatures in the South Hudson region are projected to increase between 4.1°F and 6.1°F by the 2050s and between 5.7°F and 10°F by the 2080s compared with the 1981–2010 average.

The South Hudson region is among the regions projected to experience the largest increase in the number of extremely hot days per year. Dobbs Ferry—the weather station in this region with the best long-term weather records for this climate assessment—has historically experienced an average of 18 days over 90°F; this number is projected to increase to 41 to 64 days per year by mid-century and 48 to 87 days per year by the end of the century. Days above 95°F are also expected to increase, along with the number of heat waves.

The number of cold days in the region is expected to decrease. Dobbs Ferry has historically experienced an average of 105 days below freezing (i.e., 32°F). By the middle of this century (the 2050s), Dobbs Ferry is projected to have only 54 to 82 days below freezing, and by the end of this century (the 2080s), it is projected to have only 25 to 67 days below freezing.

Total precipitation is projected to increase in the region between 4% and 11% by the 2050s and between 7% and 17% by the 2080s relative to the 1981–2010 average. This precipitation could increasingly come from heavy storms, which can lead to flooding. Dobbs Ferry has historically experienced an average of three days per year with more than two inches of precipitation; this number is projected to increase to four to five days per year by mid-century and to four to six days per year by the end of the century. Extreme precipitation may also contribute to riverine flooding and flash flooding of urban areas. 

Areas along Long Island Sound in Westchester County are vulnerable to coastal flooding. The Hudson River in this region is also influenced by ocean tides, so it is vulnerable to flooding from a combination of high streamflow and tidal flooding made worse by sea level rise. Sea level along the tidal Hudson is projected to increase by 12 to 17 inches by the 2050s and by 25 to 46 inches by the 2100s compared to a 1995-2014 baseline. This region’s location makes it one of the most exposed to hurricane risk in the state, and a combination of sea level rise and increasingly extreme storms will increase the reach of storm surge flooding.

Climate Projections and Our Actions

Projections of future climate change depend on the world’s future emissions of heat-trapping greenhouse gases. Some of the projections discussed here present a range of numbers, based on those future emissions. If global emissions are reduced, it would decrease future warming and some of the associated impacts, and the resulting climate changes could be closer to the lower numbers presented here—or even lower.

Learn more about the projections used in this assessment.

Climate Impacts to Important Regional Features

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Sea level rise in the Hudson River estuary

The Hudson River in this region is an estuary, meaning that freshwater from the river meets salt water from the ocean to create an environment that is one of the most biodiverse areas in the state. Aquatic species in these types of ecosystems are especially sensitive to changes in the concentration of salt in the water, which is likely to occur as sea level rises.

Freshwater tidal marshes along the Hudson River are likely to experience changes in habitat with sea level rise. Wetland habitats can migrate inland in response to climate change, depending on the rate of increasing tide elevations and the amount of available undeveloped land. The Hudson River could experience a net increase in wetland area if marshes are not blocked from migrating into areas higher up the riverbanks.

A brown tidal marsh along a river. A small town can be seen in the distance. Mountains line the horizon. The trees are missing their leaves.
Tidal marshes and aquatic species in the Hudson River estuary will be affected by sea level rise and changing balances of salt water.

Saltwater intrusion can occur due to gradual sea level rise or during storm surge or flood events when salt water is absorbed into surrounding soils. As water levels rise and storms become stronger, flooding will be an increasing concern for waterside communities in this region, and salt water reaching farther inland will bring added risks for nearby ecosystems, agriculture, and fresh groundwater sources.

Flooding impacts to commuter transportation

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Flooding, sea level rise, storm surge, and saltwater intrusion will create challenges to transportation systems in the region. Passenger railways along the Hudson River and Long Island Sound shoreline will be increasingly at risk of disruption and damage from flooding, erosion of supporting soils, signal malfunctions, and corrosion of equipment. Metro-North’s commuter rail line and the Amtrak trains that share this route have been shut down because of flooding. For example, in 2012, low-lying sections of track were submerged during Superstorm Sandy. More recently, in July 2023, heavy rainstorms in Westchester County caused tracks to wash out. Amtrak service between New York City and Albany was suspended until the tracks could be repaired.

A train runs on tracks along the banks of a river. A multi-lane street runs next to the train tracks, with cars parked along the street. Buildings and parks are seen directly beside the river. Mountains line the horizon. A city can be seen in the distance.
Train tracks that run along the Hudson River and are vulnerable to flooding. The station at Irvington is shown here.

The interconnected nature of rail travel also means that this mode of transportation can be disrupted by climate impacts from outside the South Hudson region. This occurred in September 2023 when flooding on Metro-North tracks between Grand Central Terminal and the Bronx led to suspended service along the Hudson, Harlem, and New Haven commuter lines.1 Another heavy rainstorm in October 2023 showed the benefits of having multiple rail options in the region. When a mudslide blocked tracks between Croton-Harmon and Tarrytown and suspended service on the Hudson line, Metro-North urged riders to use the Harlem Line, which remained operational.2

The South Hudson region is also expected to experience increased flooding and damage to roads and bridges in low-lying coastal areas. Improvements to rail and road systems, such as elevating infrastructure above projected water levels and improving drainage systems, will help reduce transportation impacts from flooding in this region.

Extreme heat and urban heat islands

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Climate projections for this region show some of the state’s largest increases in extreme heat, which can have direct impacts on people’s health. In addition to extreme temperatures, heat index is also a concern. Heat index is a measure that combines temperature and humidity. Humidity increases the danger of heat-related illness and death. During heat waves, the heat index in many regions of the state can reach “extreme caution” levels (90°F) or even “dangerous” levels (103°F) for human health, as defined by the National Weather Service. In the South Hudson region, the heat index has historically peaked at around 100°F. Maximum heat index values in the region are expected to increase throughout the century and reach “dangerous” or even “extremely dangerous” levels.

The impacts of heat are not distributed uniformly, and dense urban areas will experience higher temperatures than more rural parts of this region. This is known as the urban heat island effect, in which buildings, roads, and other infrastructure absorb more heat from the sun, leading to greater heat-related health risks in urban areas. Temperatures can even vary within urban areas due to the relative differences in infrastructure versus natural land cover. In Yonkers, for example, neighborhoods that were historically “redlined” by discriminatory mortgage practices have less tree cover and higher temperatures than other parts of the city. As a result, urban heat poses a disproportionate risk to people of color who are often still concentrated in historically redlined neighborhoods.

Buildings at sunset in the city of Yonkers.
Dense urban areas, like this neighborhood in Yonkers, will experience hotter temperatures due to the urban heat island effect.

Case Studies

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The following case studies delve into some detailed examples of impacts in the South Hudson region and ways that some communities and industries are adapting.

References

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1. Rivera, A. (2023, September 29). Aftermath of rain, floods impacted Lower Hudson Valley. LoHud. https://www.lohud.com/story/news/local/2023/09/29/hudson-valley-ny-flooding-what-to-know-severe-storms-this-weekend/71001402007/

2. Shivonne, A. (2023, October 21). Mudslide in Westchester County causes Metro-North, Amtrak service suspensions. Fox 5 New York. https://www.fox5ny.com/news/mudslide-mta-amtrak-metro-north-service-suspended

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