December 15th Marked Two-Year Anniversary of Derecho Tornadoes in North Iowa

A rare December severe weather event impacted Iowa the evening of December 15, 2021, including more than a dozen tornadoes in north Iowa.

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 was 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”, which made it the first derecho on record in the month of December anywhere in the United States. Numerous straight line wind gusts were also associated with these thunderstorms, 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 recorded by a mesonet station near Sheffield, associated with one of the tornadic circulations. 

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

Tornadoes confirmed in or near Rudd, Marble Rock (2), North Washington, Elma, Maple Leaf, Schley, Cresco, Greene, Rockwell, Hansell, Sheffield, and Meservey.