Connecticut is located on the eastern coast of the North American continent. Combined with its northerly latitude, its geographic location exposes the state to both the moderating and moistening influence of the Atlantic Ocean and the effects of hot and cold air masses from the interior of the continent. Connecticut's topography varies from hilly slopes in the northwest to diverse sections of rocky high points and marshes along the Long Island Sound of the southeastern coast. Its climate is characterized by cold, snowy winters and warm, humid summers. The jet stream, often located near the state, gives it highly variable weather patterns and generally abundant precipitation throughout the year, with annual precipitation totals ranging from 40 to 55 inches across the state (1991–2020 averages). Seasonal snowfall ranges from less than 30 inches along the coast to more than 50 inches in the Northwest Hills. Coastal areas experience warmer winters and longer frost-free seasons than inland areas. Summer high temperatures are generally around 80°F across the state, and winter low temperatures range from around 17°F in northern parts of the state to more than 25°F along the southern coast.
Time series of observed and projected temperature change (in degrees Fahrenheit) for Connecticut from 1900 to 2100 as described in the caption.
Y-axis values range from negative 4 to positive 18 degrees. Observed annual temperatures from 1900 to 2024 show variability and range from negative 3.4 to positive 4.7 degrees. By the end of the century, projected increases in temperature range from 2.0 to 8.6 degrees under the lower emissions pathway, from 4.2 to 10.7 degrees under the intermediate pathway, and from 8.6 to 17.4 degrees under the higher pathway.
Annual average temperatures in Connecticut have increased more than 3.5°F since the beginning of the 20th century (Figure 1). There is no clear trend in the number of hot days, but the highest 5-year averages were recorded for the 2010s and early 2020s (Figure 2a). The number of warm nights has shown an upward trend since the 1950s, with the highest 5-year average recorded for the 2020–2024 period at more than double the long-term average (Figure 2b). The number of very cold nights has generally been near or below average since the late 1980s, with the lowest 5-year average recorded for the 2020–2024 period (Figure 3).
Two sets of paired graphs of the observed annual number of (a) hot days and (b) warm nights for Connecticut (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
Connecticut
Y-axis values range from 0 to 16 days. Annual values range from 1.2 to 14.1 days. Five-year values are all near or below the long-term average of 6.6 days from 1950 to 2009 except for the 1955 to 1959 period. Since 2010, 5-year values are all above average. The 1975 to 1979 period has the lowest 5-year value at 5.2 days, and the 2010 to 2014, 2015 to 2019, and 2020 to 2024 periods have the highest at 8.5, 8.4, and 8.7 days, respectively.
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 1909, all near or above 36 days between 1910 and 1964, and all near or below 36 days since 1965 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
Connecticut
Y-axis values range from 0 to 20 nights. Annual values range from 1.1 to 18.4 nights. Five-year values show an upward trend across the entire period and are all near or below the long-term average of 6.4 nights between 1950 and 1999 except for the 1985 to 1989 period, but they are all above average since 2000. The 1960 to 1964 period has the lowest 5-year value at 2.1 nights, and the 2020 to 2024 period has the highest at 13.6 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 16 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 Connecticut (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.
Connecticut
Y-axis values range from 0 to 14 nights. Annual values range from 0.6 to 12.9 nights. Five-year values are near or below the long-term average of 4.4 nights between 1950 and 1959, all above average between 1960 and 1984, and all near or below average since 1985 except for the 2015 to 2019 period. The 2020 to 2024 period has the lowest 5-year value at 1.8 nights, and the 1960 to 1964 and 1980 to 1984 periods have the highest at 7.9 and 7.8 nights, respectively.
Contiguous US
Y-axis values range from 0 to 24 nights. Annual values range from 3.9 to 20.0 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.
Precipitation in Connecticut is abundant but highly variable from year to year. Statewide total annual precipitation has ranged from a low of 30.7 inches in 1965 to a high of 63.7 inches in 2011. Annual precipitation and summer precipitation have generally been near or above average since the 1970s (Figures 4a and 4b). The number of 2-inch extreme precipitation events shows no long-term trend, although the highest number of events occurred in 2011 and 2023 (Figure 5).
Two graphs of the observed total (a) annual and (b) summer precipitation for Connecticut from 1895 to 2024 as described in the caption.
Panel A: Total Annual Precipitation
Y-axis values range from 28 to 68 inches. Annual values show year-to-year variability and range from 30.7 to 63.7 inches. Five-year values also show variability and are above the long-term average of 47.4 inches between 1895 and 1904, mostly below average between 1905 and 1969, and all above average since 1970 except for the 1985 to 1989 and 2015 to 2019 periods. The 1960 to 1964 period has the lowest 5-year average at 41.0 inches, and the 2005 to 2009 period has the highest at 53.5 inches.
Panel B: Total Summer Precipitation
Y-axis values range from 4 to 22 inches. Annual values show year-to-year variability and range from 6.2 to 20.8 inches. Five-year values also show variability and are mostly above the long-term average of 12.1 inches between 1895 and 1939, all below average between 1940 and 1984 except for the 1950 to 1954 period, and all above average since 1985 except for the 1995 to 1999 and 2015 to 2019 periods. The 1910 to 1914 period has the lowest 5-year value at 9.2 inches, and the 1935 to 1939, 2005 to 2009, and 2010 to 2014 periods have the highest at 14.0, 14.1, and 14.2 inches, respectively.
Paired graphs of the observed annual number of 2-inch extreme precipitation events for Connecticut (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.
Connecticut
Y-axis values range from 0 to 7 events. Annual values range from 0.2 to 5.7 events. Five-year values are all near or below the long-term average of 2.4 events between 1950 and 1969 but are mostly near or above average since 1970. The 1960 to 1964 period has the lowest 5-year value at 1.2 events, and the 2010 to 2014 period has the highest at 3.4 events.
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 1.5 events between 1990 and 1909 but are all near or below 1.5 events between 1910 and 1989. An upward trend is evident since the early 1950s. All 5-year values since 1990 are above 1.5 events. The 1930 to 1934 period has the lowest 5-year value at 1.5 events, and the 2015 to 2020 period has the highest at 2.3 events.
Droughts are a natural part of the state's climate. Connecticut experienced extreme drought (as defined by the US Drought Monitor) in 2016–2017, 2020, and 2022, straining water supplies, impacting crop production, and increasing wildfire risk. The state experiences flash droughts (the rapid onset or intensification of drought). Although relatively short-lived, these events can often have widespread impacts on water resources, agriculture, and ecosystems.
Connecticut experiences several types of extreme events, including heat waves, cold waves, severe thunderstorms, flooding, winter storms, tornadoes, and hurricanes. The state is also affected by nor'easters—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. In 2011, Hartford was affected by an unusual snowstorm contributing to the highest-recorded January snowfall of 54.3 inches (at Hartford Bradley International Airport). Later that year, a Halloween nor'easter impacted New England with snowfall totaling more than 20 inches in some parts of Connecticut. Storm damage costs for the state, especially to power lines, were in the millions of dollars, and more than 700,000 residents lost power, with outages lasting more than a week in some areas. A blizzard in February 2013 brought heavy snowfall, which caused more than a dozen roofs to collapse. Ansonia recorded 36 inches of snow in 24 hours, breaking the state record.
Both inland and coastal flooding are a concern for the state. On August 18, 2024, a slow-moving front dropped more than 10 inches of rain in 24 hours in parts of southwestern Connecticut, leading to catastrophic flooding and three fatalities. The Great New England Hurricane of 1938 (the "Long Island Express") was the first catastrophic hurricane to impact New England since 1869, and it still holds the record for the worst natural disaster in Connecticut's history. Storm tides of 14 to 18 feet were recorded along the state's coastline, with 18- to 25-foot tides from New London east to Cape Cod. In 2012, the state experienced damaging storm surge when Superstorm Sandy (a post-tropical storm) made landfall. Coastal inundation levels ranged from 5 to 6 feet in the state, with 5.3 feet recorded at New Haven. Sandy was one of the most extreme and destructive events to affect the northeastern United States and the fifth-costliest US disaster on record. On August 4, 2020, Tropical Storm Isaias brought sustained winds of 40–50 mph to Connecticut, spun off an EF1 tornado in Westport, caused the death of one person, and left hundreds of thousands without power. 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.
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. The intensity of heat waves is projected to increase, and the intensity of cold waves is projected to decrease.
Under the intermediate emissions pathway, statistically significant increases are projected in total annual precipitation and winter precipitation (Figure 6) across the state by midcentury. There is uncertainty in projections for spring, summer, and fall precipitation. Increases are also projected in the frequency and intensity of extreme precipitation events, potentially increasing the risk of coastal and inland flooding. Coastal communities, characterized by many rivers, are particularly vulnerable to increases in precipitation and the number of extreme precipitation events.
Map of the contiguous United States showing the projected changes in total winter precipitation by the middle of the 21st century as described in the caption. A blowup map of the state of Connecticut 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.
Connecticut
The entire state of Connecticut is projected to see statistically significant increases of 10 to 15 percent in total winter precipitation.
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.
The intensity of droughts is projected to increase due to higher temperatures and the associated increase in evaporation rates and soil moisture loss. Higher temperatures and drought conditions are also expected to increase the severity, frequency, and extent of wildfires, threatening significant harm to property, human health, and livelihoods.
Like the northeastern US coast as a whole, Connecticut is at considerable risk from sea level rise. On average, the state experienced about 7 inches of sea level rise between 1970 and 2020—compared to 6 inches for the contiguous US as a whole—and projections under the Intermediate sea level scenario show additional increases of about 10 inches by 2050 and 1.6 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 3.5 feet. Rising sea levels pose a threat to the state's coastal communities, infrastructure, and ecosystems.
Two time series of observed and projected relative sea level change for (a) the contiguous US and (b) Connecticut 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 –0.3 feet in 1976 to a maximum of 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: Connecticut
All historical and future scenario lines show increases higher than those in the contiguous US graph. Tide gauge values range from a minimum of –0.4 feet in 1976 to a maximum of 0.6 feet in 2024. Satellite values range from a minimum of –0.1 feet in 1994 to a maximum of 0.5 feet in 2024. Projected sea level median values (lines) for the Low scenario range from 0.4 feet in 2020 to 1.3 feet in 2070, compared to 0.4 feet in 2020 to 3.2 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 1.0 to 1.7 feet; Intermediate-Low, 1.3 to 2.0 feet; Intermediate, 1.6 to 2.5 feet; Intermediate-High, 2.0 to 3.3 feet; and High, 2.4 to 3.9 feet.
Sea level rise 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 Connecticut as global and local sea levels continue to rise. The number of high-tide flood days has increased at New London, with the greatest number occurring in 2017. Under both the Intermediate-Low and Intermediate scenarios, high-tide floods are projected to occur much more frequently in future years (Figure 8).
Graph of the observed and projected annual number of high-tide flood days at New London, Connecticut, from 1938 to 2100 (top), including a magnified view of the observed data for the period 1938 to 2024 (bottom), as described in the caption.
A legend shows annual observations (orange bars) and projected 19-year averages (two-colored bars) for the Intermediate-Low (medium blue) and Intermediate (dark blue) sea level scenarios.
Bottom
Y-axis values for the magnified view are labeled from 0 to 10 days. Following the first recorded event in 1941, high-tide flooding was sporadic until the early 2000s, often with gaps of 1 to 2 years between events and annual values mostly below 5 days. Starting in 2005, high-tide flood days occurred every year, with a record high of 10 days in 2017.
Top
Y-axis labels range from 0 to 350 days, with a horizontal dashed gray line indicating 365 days. New London is projected to experience 50 to 65 high-tide flood days per year by 2050 under the Intermediate-Low and Intermediate scenarios, respectively, and 315 to 365 days by 2100.
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