Severe thunderstorms developed in the late afternoon, evening, and night of Friday December 10, 2021. Among strong winds and hail, several tornadoes occurred in Arkansas, Missouri, Tennessee, Kentucky, and Illinois, including multiple very strong tornadoes. The tornado outbreak was responsible for dozens of fatalities across the area, including six deaths in Illinois, many injuries, and damage or destruction to thousands of homes and structures.
Tornadoes in Illinois
As of Wednesday, December 15, the NOAA Storm Prediction Center listed 85 tornado reports from the December 10 outbreak, including 12 here in Illinois. Figure 1 shows the location of those reports (T = tornado, W = wind, H = hail). The official numbers will be released later and may vary slightly from these reports.
As of December 15, the Lincoln National Weather Service (NWS) office reports four EF-2 tornadoes affected parts of central and western Illinois on December 10 including Cass, Menard, Shelby, Moultrie, and Coles Counties. These tornadoes caused damage to homes, businesses, farm buildings, trees, and power lines. There was one injury attributed to the Shelby County tornado, but no human fatalities from these events. One horse was killed and another injured in Cass County. The Lincoln NWS office’s reports are available here: (https://www.weather.gov/ilx/December2021SvrWxUpdate).
As of December 15, the St. Louis National Weather Service (NWS) office reports two tornadoes that affected the Illinois side of their area, along with several other tornadoes on the Missouri side of the river. Among these tornadoes was an EF-3 (very strong) event around the Pontoon Beach and Edwardsville areas. The tornado struck an Amazon fulfillment center in Edwardsville, and the event was responsible for six fatalities (confirmed as of December 15) and a yet unknown number of injuries. This event was the first with tornado-related fatalities in Illinois since 2017. The EF-2 Shelby County tornado reported by the Lincoln NWS office touched down earlier in Bond County and moved through parts of Montgomery and Fayette Counties, causing damage to multiple farm buildings and trees. The St. Louis NWS office’s reports are available here: https://www.weather.gov/lsx/12_10_2021.
Parts of Arkansas, Missouri, Kentucky, and Tennessee were also hit hard by multiple, violent tornadoes that night. Details on the long-track Kentucky tornado are available on the Paducah NWS Office page: https://www.weather.gov/pah/December-10th-11th-2021-Tornado.
As of December 15, the NOAA Storm Prediction Center lists 43 wind reports from the December 10 event. The reports spanned from Grundy and Kankakee Counties in northern Illinois to Jackson County in southern Illinois. Among these are several reports of straight-line (i.e., not tornadic) wind damage to homes, farm buildings, trees, and power lines. Multiple semis were blown over in central and western Illinois.
Many of the reports of strong winds and damage are not associated with a confirmed wind gust measurement. However, those that did have a confirmed measurement include an 85 mph gust in Tazewell County that destroyed their salt dome outside of Tremont (https://www.hoiabc.com/2021/12/12/tazewell-county-highway-dept-salt-dome-damaged-storms/). A personal weather station also recorded an 80-mph gust just southeast of Decatur in Macon County.
How Rare are December Tornadoes?
We have updated the Illinois tornado climatology and plots that were originally created by Jim Angel and Michael Patrick at the University of Illinois. The plots show tornado reports across the state between 1950 and 2020, so they do not include the December 10 event.
Figure 2 shows the frequency of tornadoes by month between 1950 and 2020. About 64percent of tornadoes over that time occurred between April and June; however, tornadoes do occur outside of this time frame. For example, between 1950 and 2020, more tornadoes occurred in November and February together than in September and October together.
Figure 3 shows the number of tornado-related fatalities in Illinois by month. April is the deadliest month with 97 reported deaths, mostly due to the 58 deaths from the 1967 Oak Lawn tornado outbreak. The second deadliest month was August, mostly due to the 29 deaths associated with the August 28, 1990 Plainfield tornado.
December was the fourth deadliest month in Illinois despite having the fourth fewest tornadoes. Between 1950 and 2020, December tornadoes accounted for 3 percent of all tornadoes in Illinois, but 8 percent of all tornado-related fatalities. Similarly, Illinois tornadoes that have occurred in winter comprised 7 percent of all events between 1950 and 2020, but over 16 percent of all tornado-related fatalities.