Delaware Severe Weather - Delaware Climate Office

Extreme weather events in Delaware such as tropical cyclones, tornadoes, and mid-latitude coastal storms have been monitored for decades. The University of Delaware Center for Environmental Monitoring & Analysis (CEMA) is able to provide data on these weather events dating back into the 19th century in some cases. This data includes information on the frequency, severity, and geography of the storms. Check out the history and character of extreme weather events in Delaware below!

Coastal Storms in Delaware

Coastal storms that form in the mid-latitudes are typically characterized by strong winds, heavy rain, and in some cases coastal flooding. During the winter months, coastal storms can also be associated with heavy snowfall or ice accumulations.

Our records for coastal storms date back to 1851 for tropical systems (hurricanes and tropical storms), and back to 1945 for nor’easter type storms called mid-latitude cyclones. While coastal storms occur year-round, they are most frequent in March and generally during the spring season. There is a second peak in coastal storm frequency in late summer and early fall as tropical cyclones become more numerous.

Figure 1 shows the number of coastal storms along the mid-Atlantic coast of the United States in each month dating back to 1945. According to the data collected by CEMA, coastal storms are most common in March and least common in November. However, some of the most damaging coastal storms to affect Delaware have occurred during the autumn season.

Figure 2 This shows the number of coastal storms that have occurred along the mid-Atlantic coast of the United States each year dating back to 1945. The frequency of coastal storms has varied greatly from year-to-year with a minimum during the 1980s and larger numbers during the last decade.

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: Figure 1. This shows the number of coastal storms along the mid-Atlantic coast of the United States in each month dating back to 1945

: Figure 2. This shows the number of coastal storms that have occurred along the mid-Atlantic coast of the United States each year dating back to 1945.

Hurricanes in Delaware

A tropical cyclone is a form of extreme weather that can have devastating societal impacts.

Here, you can find a compilation of tropical cyclone (hurricanes and tropical storms) activity, that have impacted the Delmarva Region, dating back to 1851. Information about each tropical cyclone includes the storm track, intensity, and where available, detailed weather maps.

Figure 1 illustrates that tropical systems increase in frequency during the late summer and fall months in our Region, and across the entire Atlantic Basin.

Figure 2 details the frequency of tropical cyclones that have impacted Delaware every year from 1980-2020

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: Figure 1 Illustrates that tropical systems increase in frequency during the summer and fall months in Delaware

: Figure 2 Details the frequency of tropical systems that effect Delaware every year from 1980-2020

Severe Weather in Delaware

Severe weather such as strong winds, hail, and tornadoes can have a devastating impact on a community.

In this section, information on severe weather including tornadoes, hail, and strong winds can be found. Basic information on when and where these events have occurred is included.

Strong winds, usually associated with severe thunderstorms, are the most common type of severe weather in Delaware. Strong wind events are greatly under-reported because they are only noticed if they happen to occur where winds are being measured, or if they cause damage to the built or natural environment.

Figure 1 details strong wind events in Delaware from 1955 to 2020. The large upward trend apparent in these data is misleading, as reporting practices have improved tremendously over the last several decades. Still, some years stand out, such as 2016 when over 40 strong wind events were reported for Delaware, and both 2019 and 2020 which both have 80 and above reports.

Figure 2 depicts how many strong wind events have occurred in each month dating back to 1955. In Delaware, summer months (June, July, August) have had the most number of wind events.

Figure 3 illustrates the number of tornado events from 1954-2021. Tornadoes are not common in Delaware; however, when they do occur they can cause serious property damage and threaten human lives. In the data, we can observe that there are outliers, with four or more tornadoes occurring in 1966, 1975, 1992, and 2020.

Figure 4 shows the number of tornado events per month every year from 1954-2021. We can see that tornadoes form often during the summer months when the air is warm and humid. Tornado events are less common during the winter months.

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: Figure 1. Interannual number of wind events from 1955-2020

: Figure 2. Total wind events per month from 1955-2020

: Figure 3. Interannual number of tornado events from 1954-2021

: Figure 4. Total tornado events per month from 1954-2021

Hail in Delaware

Hail events in Delaware are minor compared to the size and frequency of hail in the High Plains of the United States. However, large hail does occasionally occur in Delaware and is a threat to property and agriculture. Certain conditions not common in the Mid-Atlantic region are required for large hail storms to form. Delaware averages between 2 and 3 reports of large hail events each year. However as shown in Figure 1, 2019 saw many more reports.

Figure 1 shows the frequency of hail events per year from 1968 to 2022. Before 2002, there seemed to not be as many hail events reported as 2002 to present. All of the years of five hail events or more were reported happening in 2002 and later.

Figure 2 illustrates the number of hail events per month in Delaware from 1968 to 2022. The data shows that hail events typically occur during April through August with June experiencing the most hail events.

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: Figure 1. The number of hail events in Delaware from 1968-2022

: Figure 2. The number of hail events per month in Delaware from 1968-2022

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