Weather alerts in Union County, South Dakota
3,101 weather alerts since 1986, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Union County and its neighbors
Each county as a circle sized by its count since 1986. Tap one for its archive.
- Alerts
- 3,101
- Warnings
- 1,014
- Watches
- 588
- Advisories
- 771
- Busiest year
- 2025175 alerts
- Average year
- 76over 41 years on file
Over time
By year
Before late 2005 the archive holds only tornado, severe thunderstorm, flash flood and marine warnings, and from 1997 SPC's watches, so the jump that year is the archive widening, not the weather.
By month of the year
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
From 2008 to 2025, 64% of tornado reports in Union County fell inside a tornado warning issued on average 21 minutes before, and 83% of the tornado warnings had no report inside them.
Tornado warnings by year
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| 2008 | 3 | 1 | 67% | 0 | ||
| 2010 | 2 | 0 | 100% | 0 | ||
| 2011 | 2 | 0 | 100% | 0 | ||
| 2013 | 2 | 1 | 50% | 7 | 100% | 21 min |
| 2014 | 2 | 1 | 50% | 4 | 0% | |
| 2015 | 1 | 0 | 100% | 0 | ||
| 2017 | 1 | 0 | 100% | 0 | ||
| 2018 | 1 | 0 | 100% | 0 | ||
| 2019 | 1 | 0 | 100% | 0 | ||
| 2021 | 1 | 0 | 100% | 0 | ||
| 2024 | 1 | 0 | 100% | 0 | ||
| 2025 | 1 | 0 | 100% | 0 |
Severe thunderstorm warnings by year
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| 2008 | 22 | 11 | 50% | 5 | 80% | 21 min |
| 2009 | 31 | 23 | 26% | 8 | 100% | 26 min |
| 2010 | 17 | 14 | 18% | 5 | 80% | 18 min |
| 2011 | 26 | 21 | 19% | 3 | 100% | 21 min |
| 2012 | 7 | 7 | 0% | 6 | 83% | 14 min |
| 2013 | 4 | 3 | 25% | 1 | 0% | |
| 2014 | 29 | 19 | 34% | 11 | 100% | 11 min |
| 2015 | 14 | 9 | 36% | 4 | 100% | 15 min |
| 2016 | 11 | 10 | 9% | 0 | ||
| 2017 | 16 | 12 | 25% | 5 | 80% | 24 min |
| 2018 | 5 | 3 | 40% | 1 | 0% | |
| 2019 | 5 | 4 | 20% | 2 | 50% | 23 min |
| 2020 | 19 | 19 | 0% | 11 | 91% | 24 min |
| 2021 | 16 | 15 | 6% | 4 | 75% | 5 min |
| 2022 | 23 | 16 | 30% | 12 | 92% | 24 min |
| 2023 | 23 | 17 | 26% | 14 | 93% | 24 min |
| 2024 | 11 | 8 | 27% | 10 | 60% | 31 min |
| 2025 | 25 | 20 | 20% | 18 | 89% | 19 min |
Flash flood warnings by year
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| 2008 | 3 | 2 | 33% | 1 | 100% | 9 min |
| 2009 | 9 | 4 | 56% | 0 | ||
| 2010 | 9 | 7 | 22% | 1 | 100% | 24 min |
| 2011 | 4 | 3 | 25% | 0 | ||
| 2012 | 2 | 1 | 50% | 0 | ||
| 2013 | 1 | 1 | 0% | 0 | ||
| 2014 | 2 | 1 | 50% | 0 | ||
| 2015 | 1 | 1 | 0% | 1 | 100% | 39 min |
| 2016 | 6 | 3 | 50% | 0 | ||
| 2017 | 3 | 0 | 100% | 0 | ||
| 2018 | 6 | 5 | 17% | 1 | 100% | 175 min |
| 2019 | 5 | 2 | 60% | 0 | ||
| 2020 | 2 | 1 | 50% | 0 | ||
| 2022 | 2 | 2 | 0% | 0 | ||
| 2024 | 2 | 2 | 0% | 0 | ||
| 2025 | 3 | 1 | 67% | 0 |
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.
By product
Every kind of product issued here, grouped by hazard. Each opens the same place narrowed to that product.
The latest warnings
The most recent on file, newest first.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Sep 11, 9:24 PM CDT | Severe Thunderstorm Warning | FSD | 51 min |
| Sep 1, 10:02 PM CDT | Severe Thunderstorm Warning | FSD | 43 min |
| Sep 1, 9:24 PM CDT | Severe Thunderstorm Warning | FSD | 51 min |
| Sep 1, 8:41 PM CDT | Severe Thunderstorm Warning | FSD | 49 min |
| Aug 20, 8:41 PM CDT | Severe Thunderstorm Warning | FSD | 15 min |
| Aug 12, 4:16 AM CDT | Severe Thunderstorm Warning | FSD | 37 min |
| Jul 25, 9:49 PM CDT | Severe Thunderstorm Warning | FSD | 41 min |
| Jul 25, 9:26 PM CDT | Severe Thunderstorm Warning | FSD | 34 min |
| Jul 25, 9:09 PM CDT | Severe Thunderstorm Warning | FSD | 51 min |
| Jul 25, 8:42 PM CDT | Severe Thunderstorm Warning | FSD | 48 min |
| Jul 24, 11:24 PM CDT | Extreme Heat Warning | FSD | 46 hr |
| Jul 20, 12:56 AM CDT | Extreme Heat Warning | FSD | 19 hr |
Nearby
Alerts in force nowTornadoes on recordForecastThe 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.