Debris near Lebanon, Tennessee, after tornadoes struck on the night of March 3, 2020, killing more than 20 people across the state. AP Photo/Mark Humphrey
Springtime in the U.S. is frequently a season for thunderstorms, which can spawn tornadoes. These large storms are common in the South and Southeast in March and April, then shift toward the Plains states in May. Scientists have warned that 2021 could be an active tornado year, partly because of a La Niña climate pattern in the tropical Pacific Ocean. Past research has suggested that La Niña increases the frequency of tornadoes and hail by concentrating hot, humid air over Texas and other Southern states, which helps to promote storm formation.