Tornado Season Had a Busy Start
At a Glance
- An above-average number of tornadoes was reported in March and April.
- April may be the second-most-active April since 2011 and since records began in 1950.
- This does not mean May will see more tornadoes than average.
Tornado season this spring is off to an active start with more tornadoes than average reported in March and April, but that does not mean May and June will also be above average.
In March, 145 tornadoes were reported, according to NOAA's Storm Prediction Center, including the deadly EF4 tornado that struck Lee County in Alabama on March 3. Then, 277 tornadoes were reported in April. These are preliminary numbers, as the National Weather Service is still confirming tornadoes.
The combined total of 422 preliminary tornado reports for March and April is well above the three-year average of 272 tornadoes and the 20-year average of 273 tornadoes.
If confirmed, the 277 reports of tornadoes in April would be the second-highest on record and the most since 2011. It is also well above the average of 192 tornadoes, based on data from 1998-2017.
Unsurprisingly, April 2011 saw the greatest number of tornadoes on record, with 758. Going back to 1950 when records began, the second-highest number of tornadoes in April was 267 in 1974, when a super outbreak occurred.
The weather pattern this spring has been conducive for tornado development, especially in parts of the South. Plenty of moisture has surged northward from the Gulf of Mexico at times and combined with strong disturbances, warm temperatures and strong low-level winds to allow severe thunderstorms and tornadoes to form.
There were a couple of tornado outbreaks in April, including April 17-19, when at least 95 tornadoes were confirmed in 11 states, and April 13-14, when more than 65 tornadoes in 12 states were confirmed.
Because of numerous rounds of severe weather, Alabama has already experienced more tornadoes this year than its annual average.
What About May and June?
Peak tornado season runs from April through June in the U.S. and peak activity occurs in May, when the ingredients for severe thunderstorms often come together.
The greatest threat for tornadoes is typically found in the Plains in May. Beginning in late April, that shift westward began to emerge this year.
So does an active April mean May and June will also see above-average tornado activity?
The short answer: There is no strong correlation between a busy early spring and an unusually active May or June.
From 1950-2018, nine years from have seen more than 200 tornadoes in April. Of those nine occurrences, May had below-average tornado activity (less than 279 tornadoes) six times and above-average activity three times. In addition, May had fewer tornadoes than April six of those times, as well.
When looking at June for those years with above-average tornado activity in April, six of those nine years saw below-average tornado activity. An average June sees about 213 tornadoes, based on data from 1998-2017.
However, there were a couple of years – 2009 and 1994 – that saw fewer-than-average tornadoes in May after a busy April, but then experienced more tornadoes than average in June. In 2011 and 2017, May continued the above-average tornado activity trend, but June saw fewer tornadoes than is typically expected.