List of United States tornadoes in December 2021

This page documents all tornadoes confirmed by various weather forecast offices of the National Weather Service in the United States in December 2021. In December, tornadoes are most likely in the southern states due to their proximity to the unstable airmass and warm waters of the Gulf of Mexico, with only occasional incursions farther north. The average number of tornadoes in December is 28.

After a small outbreak along with some isolated tornadoes at the beginning of the month, December unexpectedly produced two large, record-breaking tornado outbreaks during the middle of the month. The first one spawned 71 tornadoes, the most tornadoes ever recorded in a single outbreak in December. One supercell tracked over 250 mi throughout the states of Missouri, Tennessee, Arkansas, Kentucky, spawning a family of 11 tornadoes, including two violent EF4 tornadoes. The first one killed eight people across three states while the second one killed 57 people in Kentucky along a track of over 160 mi. The outbreak killed 89 people, making it the deadliest outbreak ever recorded in December. However, the record number of tornadoes set by the first outbreak was shattered just four days later by a historic derecho that produced 120 tornadoes across the Midwestern United States. The outbreak was unprecedented since tornadoes in that region during the Winter are rare, but tornadoes were confirmed as far north as southwestern Wisconsin. The derecho produced 61 tornadoes in Iowa, including 21 EF2 tornadoes, which set the record for the most tornadoes and the most EF2+ tornadoes ever recorded in the state during a single day. It also spawned tornadoes in Minnesota, marking the first time that December tornadoes had ever been recorded in the state. Some additional isolated activity and another small outbreak at the end of the month occurred before the month ended.

In all, 227 tornadoes were confirmed during December, making it by far the most active December on record as it more than doubled the previous record of 99 set in 2002. It also set the record for the most active month for tornado activity in meteorological winter, surpassing the previous record of 216 set in January 1999.