New Jersey
Figure 1
New Jersey’s geographic position in the mid-latitudes often places it near the jet stream, particularly in the late fall, winter, and spring, giving the state its characteristic varied weather. Precipitation is frequent because low-pressure storms associated with the jet stream commonly affect the state. In addition, New Jersey’s location on the eastern coast of North America exposes it to 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 the frigid air masses of the continental interior and the relatively warm Atlantic provides the energy for occasional intense storms known as nor’easters. As a result of these influences, New Jersey’s climate is characterized by moderately cold and occasionally snowy winters and warm, humid summers. There is a west-to-east contrast of temperatures, with cooler temperatures in the higher elevations of the northwest and warmer temperatures in the east near the coast. Temperature differences from the northwest to southeast are most noticeable in the winter. The northern elevated highlands and valleys experience colder temperatures and more annual average precipitation than the rest of the state. Average minimum temperatures in January range from 15° to 20°F in the northwest to 25° to 30°F along the coast. A similar temperature gradient exists for average maximum temperatures in July—cooler summertime temperatures of 80° to 85°F occur in the northwestern corner and temperatures between 85° and 90°F occur in the rest of the state. The statewide annual average precipitation is 47.6 inches. There is a north-south precipitation gradient as well, with the north-central portion of the state averaging around 50 inches of precipitation and the coastal region averaging 40–45 inches.
Temperatures in New Jersey have risen more than 3.5°F since the beginning of the 20th century (Figure 1). All of the 10 hottest calendar years on record for the state have occurred since 1990, and six have occurred since 2010. The year 2012 was the warmest on record at 3.0°F above average, and 2020 was the second warmest on record at 2.6°F above average. The number of very hot days has been varied (Figure 2a). The number of warm nights in New Jersey has consistently been above the long-term average since the early 2000s, with the highest 5-year average occurring during the 2010–2014 period (Figure 3). The number of very cold nights has been below average since the early 1990s (Figure 2b). Over the past 25 years, there have been many more unusually warm months than unusually cold months in New Jersey. During the 2000–2020 interval, there were no top 5 coldest months, but there were 38 top 5 warmest months.
Total annual precipitation for New Jersey has been about 3.7 inches above average over the last 16 years (Figure 2c). The driest conditions were in the 1960s, and near normal to wet conditions have occurred since the 1970s. The wettest consecutive 5 years was the 1971–1975 interval, and the driest was the 1962–1966 interval. The number of 2-inch extreme precipitation events was well above average during 2005–2014 but has been slightly below average since then (Figure 4). During 2010–2014, the state experienced the greatest number of 2-inch extreme precipitation events, about 50% above the long-term average. Summer precipitation has been above the long-term average during this century, with the highest 5-year average occurring during the 2010–2014 period (Figure 2d). The state can also experience short-term droughts, such as in 2002, 2010, and 2016–2017.
Figure 2
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Extreme weather events typically experienced in the state include coastal nor’easters, snowstorms, spring and summer thunderstorms, flooding rains, heat and cold waves, tropical storms, and on rare occasions, hurricanes. The state’s coastline is highly vulnerable to damage from coastal storms, which include nor’easters, tropical storms, and hurricanes. Damaging nor’easters are most common between October and April, and those tracking over or near the coast can bring strong winds and heavy precipitation. Annually, the state experiences at least one coastal storm, but some years have seen as many as 5 to 10 storm events. The most extreme and destructive event to affect New Jersey in recent years was Superstorm Sandy in 2012. The powerful storm surge, the most destructive element of Sandy, reached 9–10 feet above normal in some areas along the coast. This was caused by strong winds and an unusual west-northwestward track. New Jersey experienced extensive damage from severe winds and coastal flooding, with an estimated $29.4 billion in repair, response, and restoration costs. February 2010 brought three winter storms to the state, causing Atlantic City to have their snowiest month on record. The blizzard of 2016 brought high winds and heavy snow; Bayville, NJ, had gusts of 72 mph and many beaches experienced moderate to major erosion.
Under a higher emissions pathway, historically unprecedented warming is projected during this century (Figure 1). Even under a lower emissions pathway, temperatures are projected to most likely exceed historical record levels by the middle of this century. However, a large range of temperature increases is projected under both pathways, and under the lower pathway, a few projections are only slightly warmer than historical records (Figure 1). Increases in the number of extremely hot days and decreases in the number of extremely cold days are projected to accompany the overall warming. According to a state-level analysis, by the middle of this century an estimated 70% of summers in this region are anticipated to be hotter than what we now recognize as the warmest summer on record.
Winter and spring precipitation and extreme precipitation events are projected to increase in this century (Figure 5). The projections of increasing precipitation and heavy precipitation events are true for a large area of the Northern Hemisphere in the northern middle latitudes. This may result in increased coastal and inland flooding risks throughout the state.
Since 1900, global average sea level has risen by about 7–8 inches. It is projected to rise another 1–8 feet, with a likely range of 1–4 feet, by 2100 as a result of both past and future emissions from human activities (Figure 6). Even greater rises are projected along the New Jersey coast because of land subsidence. Sea level along the coast of New Jersey has also risen faster than the global average. Observations beginning in 1911 show sea level has risen at an average rate of 1.6 inches per decade, about double the global rate, over the period of record at Atlantic City. 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 New Jersey coastline, the number of tidal flood days (all days exceeding the nuisance-level threshold) has also increased, with the greatest number occurring in 2017 (Figure 7). Coastal flooding caused by sea level rise has important future cross-sector implications for public health, water resources, and coastal ecosystems.
