Severe Thunderstorm Warnings in Knox County, Illinois

443 severe thunderstorm warnings since 1986. An alert counts here when it covered this county. The archive of severe thunderstorm warnings reaches back to 1986.

Knox County and its neighbors

Each county as a circle sized by its count since 1986. Tap one for its archive.

Severe Thunderstorm Warnings: 443
Busiest year: 202435 severe thunderstorm warnings
Average year: 11over 40 years on file

Over time

By year

Before October 2007 these were issued for whole counties, and a storm crossing three counties was often three warnings; since then one polygon follows the storm. The count changed with the practice, not only with the weather.

Warning verification

How often warnings here had a storm report inside them, and how much warning the reports had.

From 2008 to 2025, 79% of hail, wind and damage reports in Knox County fell inside a severe thunderstorm warning issued on average 20 minutes before, and 52% of the severe thunderstorm warnings had no report inside them.

Severe thunderstorm warnings by year

	Warnings	With a report	False alarm ratio	Reports	Inside a warning	Mean lead time
2008	23	10	57%	14	86%	20 min
2009	19	12	37%	18	78%	28 min
2010	25	13	48%	12	75%	14 min
2011	15	6	60%	18	67%	20 min
2012	8	3	63%	7	86%	12 min
2013	8	4	50%	5	40%	19 min
2014	10	2	80%	6	33%	19 min
2015	11	6	45%	16	88%	26 min
2016	7	4	43%	8	50%	18 min
2017	15	10	33%	22	82%	17 min
2018	7	3	57%	6	67%	10 min
2019	18	7	61%	8	100%	26 min
2020	17	11	35%	12	92%	17 min
2021	5	3	40%	8	100%	15 min
2022	7	2	71%	4	50%	24 min
2023	21	12	43%	13	92%	28 min
2024	35	12	66%	10	90%	18 min
2025	13	6	54%	5	80%	15 min

Years from 2008, the first full year of storm-based warnings. The year still running is on its own page.

Verified by the Iowa Environmental Mesonet's Cow, which matches each storm-based warning with the local storm reports inside its polygon while it was in force, within 15 km of its edge: a tornado warning counts as verified on a tornado report, a severe thunderstorm warning on hail of 1 inch or more, a gust of 58 mph or more, or wind damage, a flash flood warning on a flash flood report. The false alarm ratio is the share of warnings with no such report; "inside a warning" is the probability of detection, the share of reports that fell inside one; lead time runs from the warning's issue to each report inside it, counting zero for a report that came first. A warning with no report is not proof nothing happened: reports come from spotters, the public and damage surveys, and are thin where few people live.

The latest severe thunderstorm warnings

The most recent on file, newest first.

Issued	Product	Office	Lasted
Aug 12, 7:44 AM CDT	Severe Thunderstorm Warning	ILX	61 min
Jul 20, 12:37 PM CDT	Severe Thunderstorm Warning	ILX	53 min
Jun 17, 8:14 AM CDT	Severe Thunderstorm Warning	ILX	61 min
Jun 11, 5:12 PM CDT	Severe Thunderstorm Warning	ILX	48 min
Jun 11, 11:47 AM CDT	Severe Thunderstorm Warning	ILX	43 min
Jun 10, 8:53 PM CDT	Severe Thunderstorm Warning	ILX	52 min
Jun 10, 7:24 PM CDT	Severe Thunderstorm Warning	ILX	66 min
Jun 10, 1:34 PM CDT	Severe Thunderstorm Warning	ILX	26 min
May 16, 4:45 AM CDT	Severe Thunderstorm Warning	ILX	33 min
May 4, 7:42 PM CDT	Severe Thunderstorm Warning	ILX	33 min
May 4, 7:19 PM CDT	Severe Thunderstorm Warning	ILX	41 min
May 4, 6:27 PM CDT	Severe Thunderstorm Warning	ILX	24 min

Nearby

Alerts in force now Tornadoes on record Forecast The radar archive

Sources

National Weather Service watches, warnings, advisories and statements from the Iowa Environmental Mesonet's VTEC archive, which reconstructs tornado, severe thunderstorm, flash flood and marine warnings back to 1986 from the NWS text archive. Storm Prediction Center watches and mesoscale discussions from SPC's archive through the Mesonet. County centers from the US Census Bureau. Warning verification from the Mesonet's Cow. Rebuilt daily.