New Hampshire's northerly latitude and geographic location on the eastern edge of North America expose the state to the moderating and moistening influence of the Atlantic Ocean, as well as to hot and cold air masses from the interior of the continent. Its climate is characterized by cold, snowy winters and mild summers. Midlatitude storm tracks and the proximity of the jet stream also influence the state's weather patterns, often resulting in highly variable conditions in the late fall, winter, and spring. The northern and western portions of the state are the least influenced by the moderating effects of the Gulf of Maine and thus experience more extreme low temperatures. The southeastern part of the state, with its lower elevations and proximity to the Atlantic Ocean, is somewhat warmer. Winter low temperatures range from more than 15°F in the south to less than 5°F in the far north (1991–2020 averages). Higher elevations are even colder, and Mount Washington regularly experiences sub-zero conditions, with temperatures reaching as low as −47°F. Summer high temperatures range from the mid-70s in the north to the low 80s in the south. The statewide annual average precipitation is 47.9 inches. Most of the state receives 45–50 inches, with higher amounts in the White Mountains.
Time series of observed and projected temperature change (in degrees Fahrenheit) for New Hampshire from 1900 to 2100 as described in the caption.
Y-axis values range from negative 4 to positive 20 degrees. Observed annual temperatures from 1900 to 2024 show variability and range from negative 3.3 to positive 4.9 degrees. By the end of the century, projected increases in temperature range from 2.6 to 9.1 degrees under the lower emissions pathway, from 4.7 to 11.1 degrees under the intermediate pathway, and from 9.2 to 18.4 degrees under the higher pathway.
Annual average temperatures in New Hampshire have increased almost 3.5°F since the beginning of the 20th century (Figure 1). The number of hot days varies widely from year to year but has mostly been above average since the 2010s (Figure 2a). Excessive nighttime heat is rare, but the number of warm nights has generally been above average since the early 2000s, with the 2020–2024 period having the highest 5-year average of about 2 nights per year (Figure 2b). The greatest warming has occurred in the winter, with an increase of more than 4°F since 1900. This is reflected in a mostly below-average number of very cold nights since the 1990s (Figure 3). The 2020–2024 period had the lowest 5-year average of fewer than 12 nights per year. Warmer winters are also reflected in a trend toward earlier ice-out dates on lakes and fewer nights below freezing.
Two sets of paired graphs of the observed annual number of (a) hot days and (b) warm nights for New Hampshire (top) from 1950 to 2024 and for the contiguous United States (bottom) from 1900 to 2024 as described in the caption.
Annual and 5-year values show variability in all graphs.
Panel A: Hot Days
New Hampshire
Y-axis values range from 0 to 20 days. Annual values range from 0.6 to 16.9 days. Five-year values are mostly below the long-term average of 6.1 days between 1950 and 2009 but are all above average since 2010. The 1965 to 1969 period has the lowest 5-year value at 4.2 days, and the 2020 to 2024 period has the highest at 8.9 days.
Contiguous US
Y-axis values range from 20 to 60 days. Annual values range from 20.7 to 57.7 days. Five-year values are below 34 days between 1900 and 1919, all near or above 36 days between 1910 and 1959, and all near or below 36 days since 1960 except for the 2010 to 2014 and 2020 to 2024 periods, which are slightly above 36 days. The 1965 to 1969 period has the lowest 5-year value at 29.6 days, and the 1930 to 1934 and 1935 to 1939 periods have the highest at 48.2 and 46.7 days, respectively.
Panel B: Warm Nights
New Hampshire
Y-axis values range from 0 to 4 nights. Annual values range from 0 to 3.0 nights. Five-year values are mostly below the long-term average of 0.7 nights between 1950 and 1999 but are all above average since 2000. The 1950 to 1954 period has the lowest 5-year value at 0.1 nights. The 2020 to 2024 period has the highest at 2.0 nights.
Contiguous US
Y-axis values range from 4 to 28 nights. Annual values range from 7.5 to 26.2 nights. Five-year values are mostly near or below 16 nights between 1900 and 1994. Exceptions include the 1930 to 1934 and 1935 to 1939 periods with more than 18 nights. An upward trend is evident since the 1970 to 1974 period, which has the lowest 5-year value at 12.1 nights. All 5-year values since 1995 are above 18 nights. The 2010 to 2014 period has the highest 5-year value at 20.4 nights.
Paired graphs of the observed annual number of very cold nights for New Hampshire (top) from 1950 to 2024 and for the contiguous United States (bottom) from 1900 to 2024 as described in the caption.
Annual and 5-year values show variability in both graphs.
New Hampshire
Y-axis values range from 4 to 44 nights. Annual values range from 6.6 to 40.7 nights. Five-year values are below the long-term average of 23.8 nights for the 1950 to 1954 period, all above average between 1955 and 1989, and all near or below average since 1990. The 2020 to 2024 period has the lowest 5-year value at 11.3 nights, and the 1975 to 1979 period has the highest at 33.4 nights.
Contiguous US
Y-axis values range from 0 to 24 nights. Annual values range from 3.9 to 20 nights. Five-year values are all near or above 10 nights between 1900 and 1989 but are all below 10 nights since 1990 except for the 2010 to 2014 period. The 2020 to 2024 period has the lowest 5-year value at 7.6 nights, and the 1915 to 1919 and 1975 to 1979 periods have the highest at 15.1 and 15.6 nights, respectively.
Statewide total annual precipitation has ranged from a low of 32.7 inches in 1941 to a high of 61.1 inches in 2005 (Figure 4a). Annual precipitation has mostly been near or above average since the 1970s, with increases across all four seasons. Summer precipitation (Figure 4b) has increased the most in recent years, with near- or above-average totals observed over 2005–2024. While the statewide average number of 2-inch extreme precipitation events shows no clear trend, the highest 5-year averages were all recorded since the late 1990s (Figure 5). Data for some individual observing stations do show trends in extreme precipitation metrics, particularly for events with more than 4 inches falling over 48 hours. New Hampshire has also been experiencing more short-term dry periods, with extreme droughts (as defined by the US Drought Monitor) occurring in 2016, 2020, and 2022.
Two graphs of the observed total (a) annual and (b) summer precipitation for New Hampshire from 1895 to 2024 as described in the caption.
Panel A: Total Annual Precipitation
Y-axis values range from 28 to 64 inches. Annual values show year-to-year variability and range from 32.6 to 61.1 inches. Five-year values also show variability and are mostly below the long-term average of 44.5 inches between 1895 and 1969 but are all near or above average since 1970 except for the 1985 to 1989 period. The 1910 to 1914 period has the lowest 5-year value at 38.2 inches, and the 2005 to 2009 period has the highest at 56.0 inches.
Panel B: Total Summer Precipitation
Y-axis values range from 6 to 22 inches. Annual values show year-to-year variability and range from 7.6 to 21.1 inches. Five-year values also show variability and are all near or below the long-term average of 12.2 inches between 1895 and 1984 except for the 1915 to 1919 period, but they are all near or above average since 1985 except for the 2000 to 2004 period. The 1910 to 1914 period has the lowest 5-year value at 9.9 inches, and the 2005 to 2009 period has the highest at 16.4 inches.
Paired graphs of the observed annual number of 2-inch extreme precipitation events for New Hampshire (top) from 1950 to 2024 and for the contiguous United States (bottom) from 1900 to 2024.
Annual and 5-year values show variability in both graphs.
New Hampshire
Y-axis values range from 0 to 5 events. Annual values range from 0.3 to 4.7 events. Five-year values are all near or below the long-term average of 1.8 events between 1950 and 1994 but are mostly above average since 1995. The 1955 to 1959 period has the lowest 5-year value at 0.8 events, and the 1995 to 1999 and 2005 to 2009 period have the highest at 2.7 and 2.8 events, respectively.
Contiguous US
Y-axis values range from 1.0 to 3.0 events. Annual values range from 1.1 to 2.5 events. Five-year values are above 1.7 events between 1990 and 1909 but are all near or below 1.7events between 1910 and 1989. An upward trend is evident since the early 1950s. All 5-year values since 1990 are above 1.7 events. The 1930 to 1934 period has the lowest 5-year value at 1.5 events, and the 2015 to 2019 period has the highest at 2.3 events.
Extreme weather events common to New Hampshire include winter storms, cold waves, thunderstorms, and extreme precipitation and flooding. The state's coastline is also highly vulnerable to damage from nor'easters and tropical cyclone events (hurricanes and tropical storms). Nor'easters are cold-season coastal storms that can generate a tremendous amount of precipitation (in the form of snow, sleet, or freezing rain), strong winds, coastal flooding, and damage to infrastructure. Tropical cyclones often result in wide-scale flooding, property damage, and coastal erosion. In August 2020, the remnants of Hurricane Isaias brought winds of more than 50 mph, leading to widespread power outages and the death of one person from a falling tree. Superstorm Sandy, in 2012, was one of the most extreme and destructive events to affect the northeastern United States and the fifth-costliest US disaster on record. The most destructive element of Sandy (a post-tropical storm when it impacted the state) was the associated storm surge, with heights reaching 3.2 feet above normal tide levels in New Hampshire. The state suffered more than $75 million in economic losses. The number of landfalling Atlantic hurricanes is not expected to rise. However, rainfall rates from such storms, as well as the proportion of time they spend as major hurricanes, are projected to increase.
Winter storms are an important feature of New Hampshire's climate. In most years, several storms depositing 5 or more inches of snow affect the state. A storm in February 2023 brought snow, high winds, and bitter cold, with Mount Washington recording a wind chill temperature of –108°F, the coldest wind chill ever recorded in the United States. Across southern portions of the state, seasonal snowfall totals for 2014–15 were well above the long-term average of about 60 inches; for example, Concord received more than 90 inches. Concord also received more than 85 inches during the winters of 2016–17 and 2017–18. Despite the high totals in those three seasons, overall snowfall has been declining in a majority of locations in New Hampshire. During the 2019–20 and 2021–22 seasons, Concord received less than 50 inches. The number of days with snow cover is also decreasing throughout the state.
Under the intermediate and higher emissions pathways, historically unprecedented warming is projected during this century (Figure 1). Even under the lower emissions pathway, most projections show annual average temperatures exceeding historical levels by the middle of the century. However, projections for all three pathways show a large range of potential temperature increases, and some projections for the lower pathway are comparable to recent observed values. Heat waves are projected to increase in intensity, while cold waves are projected to become less intense. In response to cold-season warming, the state can expect more precipitation falling as rain rather than snow, earlier lake ice-out dates, and a decline in days with snow cover. This has implications for ecosystems, water resources, and winter tourism.
Under the intermediate emissions pathway, statistically significant increases are projected in total annual precipitation and winter precipitation (Figure 6) across the state by midcentury. Statistically significant increases are also projected for spring precipitation in the northern third of the state. There is uncertainty in projections for summer and fall precipitation. The frequency and intensity of extreme precipitation events are also projected to increase, potentially increasing the risk of flooding.
Map of the contiguous United States showing the projected changes in total winter precipitation by the middle of this century as described in the caption. A blowup map of the state of New Hampshire appears to the right of the contiguous US.
Legend values range from less than negative 10 to greater than positive 15 percent. Note: unless otherwise specified, projected values are not statistically significant.
New Hampshire
The entire state of New Hampshire is projected to see statistically significant increases in total winter precipitation of 10 to 15 percent.
Contiguous US
Projected increases in total winter precipitation are as follows: up to 5 percent across a narrow swath running westward from western Georgia to southern California; 5 to 10 percent in the Southeast, Mid-Atlantic, southern Midwest, portions of the Great Plains, and most of the West; and 10 to 15 percent in the majority of the Northeast and upper Midwest as well as portions of the northern Great Plains and Intermountain West, with statistically significant increases in the 10 to 15 percent range for the Northeast, the northernmost regions of the upper Midwest, and portions of the northern Great Plains.
Projected decreases are as follows: up to 5 percent for southern regions of the Southwest and northern and central Texas; 5 to 10 percent for southern New Mexico and western Texas; and 5 to 10 percent or greater for southwestern Texas.
Naturally occurring droughts are projected to increase in intensity due to higher temperatures and the associated increase in evaporation rates and soil moisture loss.
Like the northeastern US coast as a whole, New Hampshire is at considerable risk from sea level rise. On average, the state experienced about 6 inches of sea level rise between 1970 and 2020—similar to that for the contiguous US as a whole—and projections under the Intermediate sea level scenario show additional increases of about 9 inches by 2050 and 1.5 feet by 2070 (Figure 7). Across the five scenarios shown in Figure 7, the projected increases from 2020 to 2070 range from about 0.5 to 3 feet. Coastal communities and ecosystems in Portsmouth are particularly vulnerable to sea level rise and coastal storm surge. Sea level rise also has caused an increase in high-tide floods associated with nuisance-level impacts, which are occurring more frequently, even on sunny days. High-tide flooding occurs when one or more factors—sea level rise, winds, changes in ocean currents, full or new moons—push water levels above the normal high-tide mark. These events can damage infrastructure, cause road closures, and overwhelm storm drains. High-tide flooding has increased in all US coastal areas, with more rapid increases along the East and Gulf Coasts, and is likely to occur more frequently in New Hampshire as global and local sea levels continue to rise.
Two time series of observed and projected relative sea level change for (a) the contiguous US and (b) New Hampshire from 1970 to 2070 as described in the caption.
Y-axis values range from negative 1 to positive 4 feet for both graphs. Legends in both graphs denote sources of historical data and scenarios for projections. Line colors for historical data are black for tide gauge data and orange for satellite data. Line and shading colors for projections based on five scenarios are as follows: light blue, Low; medium blue, Intermediate-Low; dark blue, Intermediate; yellow, Intermediate-High; and dark orange, High.
Panel A: Contiguous US
Tide gauge and satellite data generally show increases but with year-to-year variability. Projected data show increases under all scenarios. Tide gauge values range from a minimum of negative 0.3 feet in 1976 to a maximum of positive 0.4 feet in 2023. Satellite values range from a minimum of 0.0 feet in 1994 to a maximum of 0.4 feet in 2023. Projected sea level median values (lines) for the Low scenario range from 0.3 feet in 2020 to 1.1 feet in 2070, compared to 0.4 feet in 2020 to 3.1 feet in 2070 for the High scenario. Likely ranges (shading) become wider over the period shown. The range of likely values in 2070 for each of the five scenarios are as follows: Low scenario, from 0.9 to 1.4 feet; Intermediate-Low, 1.2 to 1.7 feet; Intermediate, 1.5 to 2.2 feet; Intermediate-High, 1.8 to 3.1 feet; and High, 2.4 to 3.8 feet.
Panel B: New Hampshire
Both historical lines show increases higher than those in the contiguous US graph, while future scenario lines show lower increases for the High and Intermediate-High scenarios and similar increases for the Intermediate, Intermediate-Low, and Low scenarios. Tide gauge values range from a minimum of negative 0.3 feet in 1976 to a maximum of positive 0.5 feet in 2023. Satellite values range from a minimum of negative 0.1 feet in 1994 to a maximum of positive 0.6 feet in 2024. Projected sea level median values (lines) for the Low scenario range from 0.3 feet in 2020 to 1.1 feet in 2070, compared to 0.4 feet in 2020 to 2.9 feet in 2070 for the High scenario. Likely ranges (shading) become wider over the period shown. The range of likely values in 2070 for each of the five scenarios are as follows: Low scenario, from 0.8 to 1.5 feet; Intermediate-Low, 1.1 to 1.9 feet; Intermediate, 1.4 to 2.3 feet; Intermediate-High, 1.7 to 3.1 feet; and High, 2.1 to 3.7 feet.
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