New Hampshire’s Climate: Signs of Change
New Hampshire’s once-predictable climate is shifting in noticeable ways. Average temperatures in the Granite State have warmed about 3°F since 1901, with the most rapid warming in winter and at night . Residents are experiencing milder winters – fewer bitter cold days and more frequent thaws – and hotter summers that drive up air conditioning use . In fact, the state has seen a 74% increase in annual cooling degree days (a measure of demand for air conditioning) since the 1970s as summers grow warmer . Correspondingly, heating needs have lessened; heating degree days have dropped about 10% since 1971 . These trends echo the lived experience of many Granite Staters: winter ice on windowpanes is rarer, summer heat waves are less of a novelty and more a regular concern.
Precipitation patterns are changing as well. Annual rainfall has increased ~12% over the past 120 years, driven largely by more frequent heavy downpours in recent decades . Simply put, when it rains, it pours – multi-inch rainstorms have become more common, especially near the Seacoast and White Mountains . This has translated into more frequent flooding of rivers and low-lying areas. New Hampshire has suffered a spate of flooding disasters in the 21st century, from the “Mother’s Day” floods of 2006 to tropical storm impacts like Irene in 2011, and numerous flash floods in between. State records show that flooding is the most common and costly natural disaster in New Hampshire . In 2023, the state experienced its wettest year on record, as relentless rainstorms drenched the region . While overall rainfall is up, short-term droughts can still occur – but intriguingly, the past few decades have seen fewer summer drought periods compared to the early 20th century , likely because of the surge in rainfall. Weather whiplash between extremes is increasingly the norm.
Winter is where climate change’s impacts are perhaps most palpable. Snowpack is dwindling and the cold season is shrinking. Measurements in central New Hampshire show the amount of water held in winter snowpack has plunged by 59–91% since 1971 – a staggering decline that speaks to thinner, shorter-lived snow cover. Residents of lakefront communities have noticed that ice-out dates on big lakes like Winnipesaukee are now about 8–11 days earlier in spring than they were in the 1970s . The iconic New England winter is literally melting away faster each year. Long-term forest monitoring at Hubbard Brook in the White Mountains has documented that winters are about two weeks shorter than they were 50 years ago . Snowpack now melts almost two weeks earlier than in past decades , and the period between winter and spring – the so-called “mud season” – has lengthened. These changes disrupt ecosystems and human activities alike. Without deep snow insulating the ground, soils freeze more often, which can damage tree roots and affect forest health . Maple sugaring season has become less reliable, since warmer winters yield less sap – hurting New Hampshire’s maple syrup producers . The traditional rhythms of tapping trees in late winter and boiling sap into syrup are being upended by shorter, erratic winters.
Wildlife across New Hampshire is responding to the warming climate – in some cases, dramatically. Moose, an iconic species of the North Country, are under siege from hordes of winter ticks that thrive when winters are mild. Shorter, milder winters have led to booming tick populations that latch onto moose by the tens of thousands . The result is often lethal for moose calves. Biologists have observed an alarming trend in northern New Hampshire and Maine: from 2014 to 2016, about 70% of radio-collared moose calves died from anemia and weakness caused by winter tick infestations . Adult moose infested with ticks become ghostly thin, often losing their dark fur in patchy clumps as they scratch at the parasites.
A “ghost moose” in New Hampshire showing significant fur loss due to thousands of winter ticks. Climate change – through shorter winters and later snowfall – lengthens the tick season and imperils the region’s moose . Studies found that in recent years, winter tick infestations killed around 70% of moose calves in parts of New Hampshire and Maine . These beleaguered moose have become a symbol of how a warming climate can upset natural balances. “It’s not a polar bear, but it’s damn close,” one New England wildlife ecologist said, noting that moose are becoming climate change indicators for the region . Other species are also on the move: bird migration and breeding cycles are shifting, and historically southern species (like opossums or certain ticks and forest pests) are extending their range northward as New Hampshire’s climate becomes more hospitable to them.
Forests and farms feel the impacts too. Warmer conditions have allowed invasive pests like the hemlock woolly adelgid to survive winters and spread into New Hampshire’s forests, killing hemlock trees that once were protected by deep freezes . Deer populations are gaining an edge in reduced snow conditions – with shallower snow, deer can roam and graze more widely in winter, which damages young forest growth and spreads a brain parasite lethal to moose via deer droppings . Farmers, for their part, are adjusting to a growing season that is now 2 to 5 weeks longer than it was just a few decades ago . A longer frost-free period might seem beneficial, but it comes with strings attached: new pests, greater weather variability, and altered timing for planting and harvest. Fruit growers have noted that earlier spring thaws can cause fruit trees to bloom early, only to be hit by a late frost. Meanwhile, intense downpours can erode soils and flood fields, and summer heat stress can affect crops and livestock. Maple syrup producers are particularly worried – the industry’s viability may decline as the climate warms, because the ideal freeze-thaw cycle for sap flow is becoming less reliable . Some projections suggest the heart of maple sugaring may eventually shift northward out of southern New Hampshire if warming continues.
Tourism and outdoor recreation – critical pieces of New Hampshire’s economy and identity – are already contending with the changing climate. Winter recreation is a prime example. Ski areas are seeing shorter, more fickle winters, which threatens an industry that draws nearly 3 million visitor-days and over $500 million annually to the state . Snow is no longer a given on Christmas or school vacations, and ski resorts have had to lean heavily on snowmaking to cover trails. During the exceptionally warm, low-snow winter of 2015–2016, New Hampshire ski visitation dropped 25% compared to the ten-year average . That winter was a wake-up call: it featured rain and bare ground during what should have been peak ski season. Ski New Hampshire, the industry association, notes that natural snow cover days are strongly tied to skier visits – when nature doesn’t cooperate, business falls off . Beyond alpine skiing, other winter activities like snowmobiling, snowshoeing, and ice fishing have also been impacted by unreliable snow and ice conditions. Organizers of winter carnivals or sled dog races now frequently worry about thaws and rainouts. Even New Hampshire’s famous fall foliage could face changes: warmer, drier late-summer conditions (or unseasonal storms) can dull the vibrant leaf colors or alter the timing of peak foliage, potentially affecting leaf-peeping tourism in the future.
Meanwhile, heavy rainfall and flooding pose challenges year-round to infrastructure and outdoor pursuits. Popular hiking trails in the White Mountains have suffered washouts from stronger downpours. Campgrounds and lakefront cottages see higher lake levels and flash flood risks. And on the Seacoast, coastal flooding is becoming a more frequent concern during storms and seasonal high tides.
What Science Forecasts for the Granite State
As notable as current changes are, scientists warn that more profound impacts are on the horizon for New Hampshire as greenhouse gas emissions continue to warm the planet. Climate projections for the state consistently point to hotter summers, milder winters, heavier rains, and rising sea levels in the coming decades .
One of the starkest shifts will be in heat and extreme temperatures. Historically, New Hampshire’s summers are moderate – for example, Concord (central NH) averaged only about a dozen days above 90°F per summer in recent decades . But that baseline is shifting upward. Climate models project that **by late-century, the state could see 50 to 60 days per year above 90°F under a high-emissions scenario . In other words, the number of very hot days could increase fivefold compared to the late 20th century. “Without reduction in greenhouse gas emissions, we’re going to be seeing a lot more of these days above 90,” warns Mary Stampone, the New Hampshire State Climatologist . Even under more optimistic scenarios where global emissions are curbed, significant warming is expected through mid-century – meaning the 2040s and 2050s in New Hampshire will be considerably warmer than today . By some estimates, if high emissions continue unabated, southern New Hampshire’s climate by 2100 could resemble what North Carolina’s climate is like today – a markedly hotter environment, with many more sweltering summer days. Heat waves that are unheard of today (such as weeks of 90°F-plus weather) could become a periodic summer occurrence. Nights, too, are projected to warm significantly, which is concerning because hotter nights (with temperatures staying above 70°F) impede cooling off and sleep , and increase health risks during heat waves.
In winter, the warming trend means extreme cold will become increasingly rare. The frequency of nights dropping below 0°F will decline sharply. Snow cover will continue to contract. Climate models downscaled for New Hampshire show a dramatic loss of snow by late century: Currently, the state averages on the order of 100 days per winter with at least 6 inches of snow on the ground in northern areas . By 2100, that could shrink to under 60 days if the world follows a lower-emissions path – or barely a month of snow cover under a high-emissions path . In practical terms, ski season could become a fraction of what it is today. A recent state climate assessment projected that by late century the “snow season” may last less than one month in a high warming scenario – essentially, a fleeting window around January. Such changes would upend winter recreation and also impact water resources, since snowpack currently acts as a natural reservoir releasing water in spring. Less snowpack and more winter rain would alter spring river flows and could increase flood risk during winter thaws.
New Hampshire is also expected to grow wetter overall, with more precipitation annually and more of it coming in intense bursts. The latest projections estimate a 16–19% increase in annual precipitation by later this century, compared to late-20th-century averages . Critically, the state is looking at a future with much heavier downpours: scientists forecast a two- to three-fold increase in the frequency of extreme precipitation events (the kind of torrential rainstorms that can cause flash flooding) by 2100 . With warmer air holding more moisture, storms are projected to unleash more rainfall. This raises concerns about flooding, erosion, and strain on dams and culverts. Even as total precipitation rises, there’s an interesting seasonal nuance: summers might not get much wetter. Models show little change in summer rainfall in New Hampshire , even as summers warm, which would mean more evaporation and periodic drought stress in summer despite wetter years overall . In effect, the state could see **wetter winters and springs, but also more frequent short-term summer droughts – a contrast that will challenge water management.
One of the most visible future impacts will be along New Hampshire’s small but populous Seacoast. Sea levels are rising, and the latest scientific guidance suggests the rise will accelerate in coming decades. Tide gauge records at Portsmouth already show that the local sea level has been rising about 0.7 inches per decade through the 20th century . But as ice sheets melt and oceans warm (expanding water), projections indicate much higher seas by 2100. New Hampshire’s Coastal Risk assessments currently advise planning for around 1.6 to 6.6 feet of sea level rise by the year 2100 (from low to high scenario) . Even mid-range scenarios (assuming moderate global efforts to cut emissions) likely bring 2–3 feet of rise by century’s end . That may not sound like much, but an extra 2 or 3 feet of water permanently elevating high tides would inundate large areas of coastal marshes and lowlands. Seacoast communities like Portsmouth, Hampton, Seabrook, and Dover are at the frontline of this change. With just 1–2 feet of rise, nuisance “sunny day” tidal flooding will become far more frequent in places like Hampton’s beach neighborhood or Portsmouth’s historic South End. Under worst-case projections of 6 feet or more by 2100, devastating floods that today might occur only in a 100-year storm could become high-tide regular events . In practical terms, parts of the Seacoast not protected by higher ground would be chronically underwater. Critical infrastructure – roads, bridges, sewage plants, the Portsmouth Naval Shipyard, and more – would be inundated unless protected or elevated. Even well before 2100, storm surges riding on higher seas will exact a toll. A nor’easter or tropical system in 2050 will be topping a higher baseline sea level than a similar storm today, meaning greater coastal flood extent. Scientists recently estimated there’s a 1-in-20 chance that about 4 feet of sea level rise could occur by 2100 even if aggressive climate action is taken globally – an outcome that would redefine New Hampshire’s coastline.
The ecological makeup of New Hampshire is poised to change as the climate shifts. By mid-to-late century, we may see a northward migration of plant hardiness zones and wildlife ranges. Species that thrive in cold, alpine conditions – such as the spruce-fir forests on our mountaintops or cold-water fish like brook trout – could lose habitat as temperatures warm. The composition of the iconic New England forest is expected to gradually shift, favoring hardwoods like oaks and birches over the spruce, fir, and maple that prefer cooler climes. Peak autumn foliage might arrive later and could be less synchronized if tree species change. Additionally, the projected warming could invite new pests and invasive species, while some native species may struggle to adapt. These ecological transformations are harder to predict with precision, but they underscore that climate change is not only about weather – it will ripple through forests, wildlife, and even the look of New Hampshire’s landscapes in the long run.
Adapting and Building Resilience in the Granite State
Faced with these challenges, New Hampshire is beginning to respond on multiple fronts – from state policy planning to grassroots community action. While the state has sometimes lagged behind some New England neighbors in climate policy, there are signs of momentum. After years of inaction, New Hampshire is updating its Climate Action Plan for the first time since 2009 . The original plan, drafted in 2009, largely sat on a shelf; but in 2023, state officials received a federal grant to develop a new “Priority Climate Action Plan” aimed at cutting carbon pollution and bolstering resilience . This effort, led by the Department of Environmental Services (DES), will lay out strategies to reduce greenhouse gas emissions (in line with regional goals like net-zero by 2050) and prepare communities for impacts. The updated plan is expected to focus on things like expanding clean energy (New Hampshire already participates in the Regional Greenhouse Gas Initiative to curb power plant emissions), improving energy efficiency, electrifying transportation, and fortifying infrastructure against extreme weather . Importantly, the state is now recognizing what scientists and citizens have been saying – climate change is here, and planning for it is not optional.
At the community and regional level, adaptation efforts are well underway. New Hampshire has a strong tradition of local governance, and many cities and towns are taking climate resilience into their own hands. On the Seacoast, where the threat of sea-level rise and coastal flooding is most immediate, collaborations have formed to help towns plan ahead. The New Hampshire Coastal Adaptation Workgroup (NHCAW) is a coalition of scientists, planners, and officials that works with coastal communities to plan for rising seas and stronger storms . Through workshops and studies, they’ve helped towns like Rye, Hampton, Exeter, and Portsmouth assess vulnerabilities and identify solutions – from restoring saltmarsh buffers to redesigning flood-prone roadways. Similarly, in the Upper Connecticut River Valley (the Hanover/Lebanon region), an Upper Valley Adaptation Workgroup formed to share best practices for handling increased flooding and heat in inland communities . These regional networks recognize that no town can tackle climate resilience alone.
City governments are also stepping up. Portsmouth, for example, has emerged as a leader in climate resilience planning. The historic port city has conducted detailed studies on how to protect its low-lying neighborhoods and waterfront. One major study, Portsmouth’s Coastal Resilience Initiative, modeled future flooding scenarios and offered a menu of adaptation strategies . The findings were eye-opening: even under a “best case” emissions scenario, Portsmouth could see 2.5 feet of sea level rise by 2100, so the city is planning for that and higher. Proposed adaptation measures include constructing flood walls and tide gates, elevating roadways and critical infrastructure, enlarging culverts, and even potentially relocating or flood-proofing historic structures . The city has already taken some steps, such as installing tide valves in storm drains to prevent seawater backflow during high tides. And after an “unprecedented” flooding event in January 2024 – when an extra-high tide combined with a storm surge inundated parts of Portsmouth – the urgency has only grown.
Historic homes at Portsmouth’s Strawbery Banke Museum surrounded by floodwaters during an extreme high tide storm in January 2024. Six of the museum’s 18th-century buildings took on water in this record-breaking coastal flood, prompting new investments in flood defenses and a “sea-level-rise” fund for the site . That event illustrated the stakes for New Hampshire’s cultural heritage and economy. In its wake, Portsmouth launched a funding initiative to fortify Strawbery Banke and other vulnerable sites against future floods . State and local officials are now discussing constructing a seawall or deployable flood barrier to protect Portsmouth’s historic downtown if sea levels continue to rise.
Elsewhere on the Seacoast, towns are updating their master plans and zoning ordinances to factor in climate projections. Municipalities like Dover and Hampton have incorporated sea-level rise maps into planning, discouraging development in the most hazard-prone zones. Some communities are restoring coastal wetlands and dunes as natural buffers – for example, Hampton and Seabrook have projects to rebuild dunes that shield inland areas from storm waves. The state’s Coastal Risks and Hazards Commission, established by the legislature, issued comprehensive recommendations in 2016 for how cities and towns should prepare for projected coastal changes . Those recommendations – ranging from higher freeboard elevations in building codes to better emergency evacuation routes – are gradually being put into practice.
Inland cities like Manchester and Nashua, while not facing sea-level rise, are grappling with river flooding and urban heat. The Southern New Hampshire Planning Commission (SNHPC), which covers the Manchester area, notes that inland flooding from intense rain is the region’s most significant climate risk . To combat this, Manchester and neighboring towns are upgrading stormwater systems – for instance, upsizing culverts and storm drains to handle heavier rainfall. After severe floods in the past (such as the 2006 floods that hit southwest NH), many towns have sought federal grants to reinforce bridges and buy out homes in floodplains. Manchester has also focused on sustainability initiatives: the city has improved energy efficiency in public buildings and is developing plans for cooling centers and urban tree planting to mitigate heat waves. In July 2024, Manchester endured a record 14-day stretch of 90°F+ heat – an event that underscored the need for heat emergency plans and green infrastructure in the state’s largest city . Cities are considering steps like planting shade trees, creating cooling shelters, and using reflective “cool roofs” on buildings to ease urban heat island effects.
The rural and mountain regions are not standing idle either. In the North Country and White Mountains, local leaders are discussing how to diversify recreation and tourism in the face of shorter winters. Ski resorts have been investing in robust snowmaking systems and expanding year-round attractions (like mountain biking, zip lines, and festivals) to remain profitable as winters shorten . “With shrinking winters due to a warming climate, these off-season activities as well as improvements in snowmaking will take on greater significance,” notes Jessyca Keeler of Ski New Hampshire . The industry is banding together to share technology and advocate for policies (like energy incentives) that support snowmaking, since it’s energy-intensive. Towns in the White Mountains are also proactive in safeguarding infrastructure: for example, Lincoln and Bethlehem have strengthened riverbanks and redesigned road culverts after washouts from heavy rain in recent years. The U.S. Forest Service is incorporating climate models into its management of the White Mountain National Forest, looking at which tree species to replant and how to maintain trails under heavier rainfall. Local nonprofits and volunteers have come together to restore hiking trails damaged by extreme weather, essentially building back stronger to handle future storms.
New Hampshire’s academic and research institutions are contributing as well. The University of New Hampshire (UNH) has a Sustainability Institute that spearheaded the New Hampshire Climate Assessments and is advising communities. UNH researchers are pilot-testing nature-based solutions like restoring floodplains to absorb floodwaters, and studying saltmarsh health on the Seacoast as sea levels rise . In one $6 million project, UNH and partners are designing “living shorelines” – using natural materials like oyster reefs and salt marsh grasses – to protect the coast while preserving ecosystems . The idea is to buffer wave energy and trap sediment, helping the coast keep up with rising seas in a more sustainable way than concrete seawalls.
State agencies, for their part, have begun integrating climate resilience into their planning mandates. The New Hampshire Department of Transportation, for instance, recently completed a Transportation Resilience Plan identifying which roadways and bridges are most at risk from flooding and heat, and prioritizing them for upgrades . The Department of Health and Human Services has launched a Climate and Health Initiative to help hospitals and local health departments plan for heat waves, air quality issues, and vector-borne diseases (like Lyme disease, which may worsen with climate change). And New Hampshire’s Department of Environmental Services maintains a Climate Adaptation Plan and toolkit for municipalities , which includes guidance on everything from culvert design for 100-year storms to updating floodplain maps and conserving wetlands.
In summary, New Hampshire is awakening to its climate challenges. The impacts of climate change – once subtle – are now evident in daily life, from the slushier winter slopes at ski areas to the overflowing banks of rivers after heavy rains. Scientific projections paint a clear picture that these changes will intensify, but also offer a roadmap for preparation. The Granite State’s response is taking shape on multiple levels. As one climate expert put it, we can no longer assume the climate our grandparents knew will be the climate our grandchildren inherit; instead, that future climate depends on our choices and actions today. Through planning, innovation, and community resolve, New Hampshire is working to ensure that the state’s people, environment, and economy remain resilient – come hell or high water, or in this case, heat waves and high tides .
Sources:
Climate Assessment 2021 (UNH) ; NOAA State Climate Summaries ; Strawbery Banke Museum ; N.H. State Climatologist (NHPR) ; Appalachian Mountain Club ; Cary Institute/Hubbard Brook ; Portsmouth Coastal Resilience Report ; N.H. Coastal Adaptation Workgroup ; Conservation Law Foundation ; Southern NH Planning Commission ; UNH Extension/Climate Projections ; Cameron Wake, UNH .
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