Tornado counts are considered preliminary until final publication in the database of the National Centers for Environmental Information.
[1] Activity spreads northward and westward in May, with the maxima moving into the Midwest and the Great Plains as the springtime jet stream patterns tend to occur farther north (while the South begins to see decreasing activity), while the potential for tornadic activity also increases in the Northeastern United States.
A very sharp temperature and moisture contrast due to a weakening El Niño caused temperatures across the Plains and Midwestern United States to be cooler than normal while record-breaking heat waves continued across Texas and Mexico.
This temperature contrast led to an abnormally strong jet stream along with a marked increase in wind shear while the moisture contrast caused by a warmer than normal Gulf of Mexico led to abundant atmospheric instability.
This pattern persisted throughout the entire month and, as a result, the trend of widespread, relentless tornadic weather that started at the end of April continued into May and only two of the 31 days in the month had no confirmed tornadoes.