South Dakota experiences a distinct annual cycle of powerful thunderstorms. The state’s geography, where warm, moist air from the Gulf of Mexico collides with cool, dry air from the north and west, creates an environment conducive to tornado formation. For residents and those interested in meteorology, timely information regarding the latest confirmed tornado events is a common concern. Understanding the recency of the last confirmed event provides a practical measure of the current severe weather risk.
Identifying the Most Recent Confirmed Event
The most recent confirmed tornado in South Dakota occurred on the evening of Monday, July 28, 2025, as part of a significant severe weather outbreak involving a supercell thunderstorm that tracked across the south-central part of the state. The final confirmed tornado from this cell touched down near Bonesteel in Gregory County at approximately 6:01 PM Central Daylight Time (CDT).
The National Weather Service (NWS) survey assigned this tornado an Enhanced Fujita (EF) scale rating of EF-2, indicating estimated wind speeds between 111 and 135 miles per hour. The damage path included a single-family residence that sustained major damage, the destruction of two nearby outbuildings, and damage to several power poles. This tornado was the third confirmed one from the same storm that day, which had earlier produced an EF-1 near Dixon and an EF-0 near Lucas, all within Gregory County.
Seasonal Context and Frequency of Tornadoes
South Dakota’s tornado season is highly concentrated, with the majority of events occurring from late spring through mid-summer. The peak month for tornado activity is June, which accounts for nearly 40% of all recorded events in the state. May and July also contribute significantly to the annual total, highlighting the period when warm, moist air fuels severe thunderstorms.
The state averages about 28 to 36 confirmed tornadoes annually, placing it among the states most frequently affected by these storms. This frequency has seen a recent downward trend compared to historical figures, which is part of a broader pattern where the core of “Tornado Alley” appears to be shifting eastward.
Geographically, tornado activity is not uniform across the state. Counties in the eastern and south-central plains, like Brown and Lincoln, have recorded the highest number of touchdowns due to their position in the path of typical storm systems. Most tornadoes develop during the late afternoon and early evening hours, often peaking around 6:00 PM.
How Tornado Data is Tracked and Verified
The official confirmation and rating of a tornado event is the sole responsibility of the National Weather Service (NWS). This process begins with the issuance of warnings by local NWS offices, including those in Aberdeen, Sioux Falls, and Rapid City. Warnings are based on radar analysis showing strong rotation (a mesocyclone) and reports from trained storm spotters.
Following a reported touchdown, NWS personnel conduct a ground survey of the damage path to determine if a tornado was the cause, distinguishing it from straight-line wind damage. The intensity rating is then assigned using the Enhanced Fujita (EF) scale, which has been the standard since 2007. The EF scale ranges from EF0, the weakest, to EF5, the strongest, and is based on estimated wind speeds correlated with observed damage.
NWS surveyors examine 28 different types of structures and vegetation, called Damage Indicators (DIs), and assess their Degree of Damage (DoD). They compare the damage to a home or a tree with established guidelines to estimate the three-second wind gust that caused it. This detailed analysis ensures the final EF rating accurately reflects the maximum wind speed that occurred along the tornado’s path.