Delaware is a coastal state, but its historical exposure to direct, high-category hurricane landfalls is limited. A hurricane is classified as a tropical cyclone with sustained wind speeds of 74 miles per hour (mph) or higher. Since reliable record-keeping began, no tropical cyclone has officially struck the state while maintaining hurricane intensity at the point of impact. The state has experienced the effects of numerous tropical systems, with at least 111 tropical cyclones or their remnants affecting the region since 1749. The primary threat is the widespread damage caused by weakened storms and their associated hazards.
Geographic Factors That Mitigate Direct Hits
The primary reason Delaware rarely sees a hurricane landfall is due to the typical track of Atlantic storms. Atlantic hurricanes generally track northward along the U.S. East Coast, but many systems tend to curve, or “recurve,” away from the Mid-Atlantic and toward the open ocean or New England. This common trajectory steers the most powerful storms away from the Delaware coastline.
Even when storms approach the region, they often encounter cooler Sea Surface Temperatures (SSTs) north of the Carolinas, which acts as a natural inhibitor. Cooler water strips the storm of the energy needed to sustain hurricane status. Furthermore, many hurricanes that affect Delaware have already tracked over the large landmasses of the Carolinas and Virginia. Moving over land rapidly diminishes a hurricane’s strength, often weakening it into a tropical storm or tropical depression before it reaches the state.
The Real Threat: Tropical Storms and Inland Flooding
While direct hurricane landfalls are rare, Delaware is highly susceptible to the severe impacts of weakened tropical systems. The greatest danger from these storms is not high wind speeds, but water-related hazards, primarily widespread and prolonged heavy rainfall. Delaware’s low-lying topography and extensive network of tidal tributaries make it particularly vulnerable to flooding. These systems often stall or move slowly, leading to sustained rain events that quickly overwhelm local watersheds and result in massive inland flooding.
Along the coast, the major threat is storm surge, especially in low-lying areas like Sussex County and along the Delaware Bay shoreline. Storm surge is the abnormal rise of water generated by a storm, and it is exacerbated by the state’s very low elevation. Even a modest surge can cause extensive inundation, particularly when it coincides with a high astronomical tide. This combination of coastal surge and inland fresh-water flooding represents the most common and damaging impact of tropical systems in Delaware.
Notable Historical Storm Impacts
Historical events confirm that weakened or non-landfalling storms pose a significant threat to Delaware. Superstorm Sandy in 2012, a post-tropical cyclone when it made landfall in New Jersey, still caused extensive damage throughout the state. Sandy generated a storm surge of up to eight feet and caused severe coastal erosion. The storm resulted in widespread power outages and significant property damage.
Similarly, the remnants of Hurricane Agnes in 1972 illustrate the danger of inland flooding. Agnes weakened to a tropical storm and caused catastrophic flooding throughout the mid-Atlantic region. Its prolonged rainfall contributed to record river crests in the Delaware River basin. This event underscores how storm remnants can produce devastating, widespread damage far from the coast.