Tornadoes have the potential to strike various regions of the United States throughout the year, but the months of April, May, and June stand out as the most active in terms of thunderstorms giving rise to these destructive natural phenomena. Let’s explore some of the patterns that underline why these spring and early summer months pose a heightened risk for tornadoes.
The geographical area susceptible to tornado threats expands and shifts during the spring season. The regions at highest risk for tornadic storms gradually alter as we progress through the months. In April, much of the Deep South faces an elevated tornado threat, while the focus shifts towards the Plains and Midwest from May into June. This seasonal progression can be observed in the accompanying maps.
Historical weather data illustrates the peak in tornado activity during the spring months. Over the period from 2004 to 2023, the United States experienced an average of 1,246 tornadoes annually, with approximately 52% occurring in April, May, and June. May typically sees the highest number of tornadoes, averaging around 260, followed by April with 202, and June with 186 tornadoes per year.
The intensity of tornadoes adds to the peril during this time of year. Statistics from Dr. Greg Forbes, former severe weather expert at The Weather Channel, show that about 58% of all twisters rated F3/EF3 or stronger between 1950 and 2012 struck during these three months, increasing to 69% for tornadoes rated F4/EF4 or stronger. The majority of the most severe F5/EF5-rated tornadoes since 1950 have occurred in April, May, or June.
While all tornadoes pose a threat, the more intense ones result in a higher number of fatalities and damage. Data from NOAA’s Storm Prediction Center reveals that approximately 83% of tornado-related deaths from 2019 to 2023 were caused by tornadoes rated EF3 or stronger.
The atmospheric conditions conducive to tornado formation align most frequently during the spring season. Tornado outbreaks typically occur when a storm system, driven by a robust southward dip in the jet stream, moves into the Plains, Midwest, or South. The jet stream provides critical wind shear, essential for the development of tornadic thunderstorms, especially when paired with ample moisture drawn northward from the Gulf.
As spring progresses, the jet stream migrates northward towards the Canadian border, diminishing the tornado threat in the South by June. Conversely, the risk increases in northern regions as the jet stream and atmospheric moisture coincide more frequently later in the season.
Now is a timely opportunity to review your severe weather plan for spring and any period when tornadoes could pose a threat in your area.
