Although Maryland is not part of the traditional “Tornado Alley,” the state does experience tornado activity, and residents should remain prepared for severe weather events. Tornadoes in Maryland are generally less frequent and less intense than those in the central United States, but they still pose a risk. Understanding the state’s specific tornado history, typical severity, seasonal patterns, and alert systems is important for public awareness and preparation.
Historical Frequency and Rate of Occurrence
Maryland experiences a modest number of tornadoes annually, though the reported frequency has seen an upward trend in recent decades. From 1950 to 2022, the average number of confirmed tornadoes was approximately 5.6 per year across the state. However, the average increased to about 9.5 tornadoes per year during the more recent period from 1990 to 2022.
This increase in reported events is largely due to advancements in detection technology, such as Doppler radar, and improved documentation from trained spotters. When considering the density of tornadoes per square mile, Maryland can rank relatively high compared to other states. The concentration of events in this small, densely populated state highlights the localized risk, even though the total number is lower than the national average.
Typical Severity and Damage
Maryland tornadoes are typically weaker, with the vast majority falling into the lower classifications of the Enhanced Fujita (EF) Scale. The EF Scale rates a tornado’s intensity from EF0 to EF5 based on estimated wind speeds and the resulting damage. Most tornadoes in the state are classified as EF0 or EF1.
An EF0 tornado, with wind gusts between 65 and 85 miles per hour, causes light damage, such as peeling surface material or breaking tree branches. An EF1 tornado (86 to 110 miles per hour) causes moderate damage, including pushing cars off roads, removing sections of roofing, and uprooting trees. Major events, classified as EF3 or higher, are rare, though the state has experienced a few significant, destructive tornadoes, such as the one that struck La Plata in 2002.
Tornado Seasonality and Geographic Hotspots
Tornado activity shows a distinct seasonality, with the primary threat period running from late spring through the summer. Peak activity typically occurs between May and July, with June historically recording the highest number of events. This period features warm, moist air from the Atlantic Ocean colliding with cooler continental air masses, creating the atmospheric instability required for severe thunderstorm development.
The most common time for tornadoes is the late afternoon and early evening, between 3 p.m. and 9 p.m. Geographically, events are not evenly distributed across the state. Frederick County has historically recorded the highest number of tornadoes, followed by Baltimore and St. Mary’s counties. This concentration is often associated with the state’s varied topography, where weather systems interact with the Appalachian foothills or the moisture-rich air near the Chesapeake Bay.
The Difference Between a Tornado Watch and a Warning
The National Weather Service (NWS) uses two distinct alert levels to communicate the tornado threat, each requiring a different response. A Tornado Watch means conditions are favorable for tornadoes to form in the designated area. Watches are issued by the Storm Prediction Center, typically cover a large area, and last for several hours.
When a watch is issued, the public should remain vigilant, review emergency plans, and ensure a safe shelter is accessible. A Tornado Warning, in contrast, means a tornado has been sighted or indicated by weather radar, posing an imminent danger. Warnings are issued by local NWS forecast offices, cover a much smaller area, and usually last about 30 minutes. If a warning is issued, the public must take immediate action by moving to an interior room on the lowest floor of a sturdy building, away from windows.