Rhode Island has warmed by more than 3°F over the past century. Under a higher emissions pathway, historically unprecedented warming is projected by the end of the 21st century. Increased intensity of heat waves is also projected, but a decreased intensity of cold waves.
Both mean and extreme precipitation has increased during the last century, with the highest number of extreme events occurring over the last decade. Continued increases in frequency and intensity of extreme precipitation events are projected.
Sea level has risen more than 9 inches since 1930 at Newport, faster than the global average. It is projected to rise another 1 to 4 feet by 2100. Increases in sea level will likely increase coastal flooding and erosion during winter storms (nor’easters) and hurricanes.
Rhode Island’s geographic position in the mid-latitudes often places it near the jet stream, particularly in the late fall, winter, and spring. Its characteristic of frequently changing weather results from the regular passing of low pressure storms associated with the jet stream. In addition, Rhode Island’s location on the East Coast of North America exposes it to both the cold winter and warm summer air masses of the continental interior and the moderate and moist air masses of the western Atlantic Ocean. In winter, the contrast between frigid air masses of the continental interior and the relatively warm Atlantic Ocean provides the energy for occasional intense storms known as nor’easters. In Providence, average temperatures in July are around 74°F and in January about 29°F. Statewide annual average precipitation is about 45 inches. The driest year on record (28 inches) was 1965 while the wettest year on record (63 inches) was 1972. Average accumulated snowfall ranges between 20 inches on Block Island and along the southeastern shores of Narragansett Bay to between 40 and 55 inches in the western portion of the state.
Temperatures in Rhode Island have increased by more than 3°F since the beginning of the 20th century (Figure 1). The number of hot days (maximum temperature above 90°F) in Rhode Island has been above the long-term average since the mid-1990s with the largest number occurring during the most recent 5-year period of 2010–2014 (Figure 2). The number of warm nights (minimum temperature above 70°F) was also largest during the most recent period (Figure 3a) and very cold nights (minimum temperature below 0°F) have been below average since the mid-1990s (Figure 4).
Average annual precipitation for Rhode Island has generally been above average in recent decades. The driest multi-year periods were the 1940s and the latter half of the 1960s, and the wettest in the 2000s, although precipitation has been predominantly above average since the 1970s. The driest 5-year period was 1962–1966; the wettest 5-year period was 2005–2009 with an annual average of 54 inches, about 8 inches above the long-term average (Figure 3c) and summer precipitation has been well above average since 2000 (Figure 3d). Rhode Island has experienced the largest number of extreme precipitation events (precipitation greater than 2 inches) in the most recent decade (2005–2014) (Figure 3b). In 2010, major rainfall from a nor’easter in late March caused the worst flooding in the state’s history. This event set an all-time monthly precipitation record in Rhode Island of 16.34 inches, superseding the previous record of 15.38 inches recorded in October 2005. The flooding of 2010 resulted in an estimated $43 million in national flood insurance claims in the state.
Extreme weather events common to Rhode Island include severe storms (coastal, winter, and thunderstorms), often accompanied by flooding, and on occasion, tropical storms and hurricanes. The state’s coastline is highly vulnerable to flood damage from winter and hurricane events. FEMA disaster declarations were sought 6 out of the last 10 years, 3 of which were for severe flooding. The Northeast has been affected by 15 landfalling hurricanes since 1900, 7 of which affected Rhode Island. The Great New England Hurricane (Category 3) of 1938 was one of the most destructive and powerful storms ever to impact southern New England. Storm tides of 12 to 15 feet were recorded for Narragansett Bay and downtown Providence was submerged under a storm tide of 20 feet. In October 2012 Superstorm Sandy (a post-tropical storm) caused a storm surge 9.4 feet above normal high tide in Providence resulting in extensive coastal flooding. One year earlier, heavy rainfall and strong southeast winds—up to 70 mph—from Hurricane Irene knocked down power lines, leaving half of Rhode Island’s one million residents without power. Both hurricanes demonstrated the regions vulnerability to extreme weather events.
Under a higher emissions pathway, historically unprecedented warming is projected by the end of the 21st century (Figure 1). Even under a pathway of lower greenhouse gas emissions, average annual temperatures are projected to most likely exceed historical record levels by the middle of the 21st century. However, there is a large range of temperature increases under both pathways, and under the lower pathway, a few projections are only slightly warmer than historical records. Heat waves are projected to increase in intensity while cold waves are projected to become less intense. Rhode Islanders may experience more heat-related deaths, and hotter conditions will be most dangerous in urban areas due to the heat-island effect.
Increases in annual mean precipitation are projected for Rhode Island (Figure 5), with those increases coming in the winter and spring. Rhode Island is part of a large area of the Northern Hemisphere in the higher middle latitudes projected to see increases in precipitation, as well as increases in extreme precipitation events. Projections of more precipitation and a greater number of extreme precipitation events may also result in increased flooding risks. Although increased precipitation is projected, naturally-occurring droughts are projected to be more intense because higher temperatures will increase evaporation rates.
Since 1880, global sea level has risen by about 8 inches. Tide gauge recordings between 1931 and 2015 in Newport show an average rate of sea level rise of 2.72 mm (about 0.1 inch) per year, equivalent to more than 10 inches over a century. Sea level rise has caused an increase in tidal floods associated with nuisance-level impacts. Nuisance floods are events in which water levels exceed the local threshold (set by NOAA’s National Weather Service) for minor impacts. These events can damage infrastructure, cause road closures, and overwhelm storm drains. As sea level has risen along the Rhode Island coastline, the number of tidal flood days (all days exceeding the nuisance level threshold) has also increased, with the greatest number occurring in 2012 (Figure 6). Sea level is projected to rise another 1 to 4 feet by 2100 as a result of both past and future emissions from human activities (Figure 7) and will be accompanied by large increases in tidal flood events.
Higher sea levels will likely increase the probability for major flooding events. According to the National Flood Insurance Program, “the increase in the expected annual flood damage by the year 2100 for a representative National Flood Insurance Program (NFIP) insured property subject to sea level rise is estimated to increase by 36 to 58 percent for a one-foot rise” in sea level. Sea level rise along most of the coastal Northeast is expected to exceed the global average rise due to local land subsidence. A sea level rise of two feet, without any changes in storms, would more than triple the frequency of dangerous coastal flooding throughout most of the Northeast.