December 15, 2021: One of the Wildest Weather Days in Iowa History

*The above image is from storm damage in Franklin County in north central Iowa from December 15, 2021.

On the morning of December 15, 2021, people across Iowa woke up to temperatures well above normal. Later that day, the warmest December temperature in state history was set in not one, but four different cities. Mother Nature has a way of making you pay for those things and it didn't take her long.

Iowa City, Muscatine, Oskaloosa, and Ottumwa all reached 75 on December 15, 2021, one degree higher than the previous Iowa record high December temperature of 74 degrees, set in Thurman, Iowa on December 6, 1939. In Cedar Rapids, the low temperature was 48 that morning... 31 degrees above normal. In the afternoon, the high hit 73. It was the warmest December high temperature in the city's history.

As a storm system developed, the Storm Prediction Center set the risk of severe thunderstorms in Iowa at moderate for the first time ever in December. They couldn't have been more right. A squall line of thunderstorms would unleash a long line of severe weather. It would later be confirmed it was a derecho, the first December derecho in U.S. history.

The derecho spawned 120 tornadoes across Nebraska, Iowa, Minnesota, and Wisconsin. The Iowa numbers from December 15, 2021 are still nearly impossible to comprehend:

• 63 confirmed tornadoes. The state of Iowa had a TOTAL of 114 last year.
• The 63 tornadoes were 28 more than the previous single-day high (35) in the state, set on August 31, 2014.
• Of the 63 tornadoes, 21 were EF2 or stronger. Another Iowa record for a single day. The previous high was 16 EF2 or stronger tornadoes on June 7, 1984.

Before December 15, 2021, there had been only five December tornadoes in Iowa in the previous 61 years, dating back to 1950.

Last year's storm system made for an impressive radar loop:

In Iowa, it was our second derecho in 16 months. A third hit the state on July 5, 2022.  Here's the definition of a derecho, straight from the National Weather Service:

A derecho is "a widespread, long-lived wind storm associated with a band of rapidly moving showers and thunderstorms (squall line). Although a derecho can produce destruction similar to a tornado, the damage typically occurs in one direction along a relatively straight swath (sometimes referred to as "straight-line wind damage")."