North Dakota sits within the northern Great Plains, a position that places it in the path of colliding air masses necessary for severe weather. The state regularly experiences thunderstorms capable of producing tornadoes, especially during the warmer months. Understanding the frequency, location, and severity of these events is important for residents preparing for the annual severe weather season. This analysis focuses on the historical data and context of tornado activity in the state.
Frequency and Historical Averages
North Dakota averages approximately 29 to 32 confirmed tornadoes each year, based on recent National Weather Service (NWS) climatology data. The annual average is subject to considerable variability, with some years seeing single-digit counts and others experiencing significant outbreaks. Since formal record-keeping began, the state has documented over 1,700 tornado events.
The year-to-year count depends on specific atmospheric conditions. For instance, the state’s previous annual record of 61 tornadoes, set in 1999, was surpassed recently with a total of 73 confirmed tornadoes. An active year can see the average count more than double, often due to a single outbreak that produces numerous short-lived touchdowns.
The most active period for tornado formation aligns with the peak summer months. Historically, June is the most prolific month for tornadoes in North Dakota, followed closely by July. This pattern is typical for the Northern Plains, as the jet stream moves northward, allowing for the clash of warm, moist air from the south and cooler air from Canada.
Geographic Distribution and Peak Timing
Tornado activity is concentrated in the eastern half of the state, particularly the counties bordering Minnesota. Cass, Grand Forks, and Barnes counties consistently rank among those with the highest number of recorded events. This concentration reflects the proximity to the moisture source and the favorable terrain of the flat plains.
The western part of the state, which includes the rugged Badlands and areas with higher elevation, tends to see fewer tornadoes overall. When tornadoes do occur, they are most likely to touch down during the late afternoon and early evening hours. The peak time for tornado occurrence is around 5:00 PM local time, which is when the sun’s heating has maximized atmospheric instability.
The tornado season typically spans from May through August, though events can occur as early as March and as late as October. This limited but intense period requires heightened awareness during the summer months, as the northern climate supports the necessary severe storm ingredients.
Severity and Rating Systems
Tornado intensity is measured using the Enhanced Fujita (EF) Scale, which assigns a rating from EF0 to EF5 based on estimated wind speeds derived from the damage caused. The majority of tornadoes in North Dakota are on the lower end of the scale, typically classified as EF0 or EF1. These weaker tornadoes can still cause damage, such as snapping tree limbs, damaging sheds, and causing minor structural damage to homes.
While most are weaker, the state is not immune to violent storms. North Dakota has experienced the full spectrum of tornado intensity, including rare, powerful events. A recent major event was classified as an EF5, the highest possible rating, with estimated winds exceeding 200 miles per hour. This EF5 tornado carved a path over 12 miles and caused catastrophic damage, demonstrating the potential for devastating storms.
Local Warning Systems and Safety
The National Weather Service (NWS) offices in Bismarck and Grand Forks are responsible for issuing severe weather alerts across North Dakota. These alerts are categorized into two main types: a Tornado Watch and a Tornado Warning. A Tornado Watch indicates that atmospheric conditions are favorable for tornadoes to develop in or near the watch area.
A Tornado Warning is a far more immediate alert, signifying that a tornado has been sighted or is strongly indicated by weather radar. When a warning is issued, immediate action is required, as the threat is imminent. Residents should quickly move to a designated shelter, such as a basement or an underground storm cellar.
If an underground shelter is unavailable, the safest place is an interior room or hallway on the lowest floor, away from all windows. Residents in rural areas should have a plan for farmsteads and know that mobile homes offer very little protection from tornadic winds. Having multiple ways to receive alerts, such as NOAA weather radio and phone apps, is advised, especially since rural areas may lack audible siren coverage.