Four-Year Anniversary of December 15, 2021 Derecho Tornadoes

Monday (12.15) marks the four-year anniversary of what the National Weather Service (NWS) says was the first recorded December Derecho in United States history, spawning the most tornadoes ever in one day in Iowa, including more than a dozen in north and northeast Iowa.

NWS notes, not only was this one of the highest threats for severe weather so late in the year (December), it shattered records for the number of warnings so late in the season. Several all-time December temperature records were also set, with the warmest at 74 degrees in Thurman, Iowa. Charles City’s high that day was 68 while New Hampton only reached 55.

The storm also met the criteria for a “derecho,” with numerous straight line wind gusts, some in excess of 80 mph. Nearly the entire state of Iowa was under a Severe Thunderstorm Warning at some point.  An unofficial gust of 108 mph was recorded near Sheffield, associated with one of the tornadic circulations. 

There were 63 confirmed tornadoes that occurred in Iowa on December 15, 2021, with 21 of those being rated EF-2. The 63 twisters were the most tornadoes in Iowa in a single day, with the previous being 35 tornadoes on August 31, 2014. 

Tornadoes that record day included those confirmed in or near Rudd, North Washington, Elma, Maple Leaf, Schley, Cresco, Greene, Rockwell, Hansell, Sheffield, and Meservey, plus two at Marble Rock.