Weather alerts in South Dakota, 2019
2,541 weather alerts in 2019, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered any part of the state, so the counties below add up to more than the state.
Weather alerts by county
Each county as a circle sized by its count in 2019. Tap one for its archive.
- Alerts
- 2,541
- Warnings
- 1,239
- Watches
- 121
- Advisories
- 291
- Busiest month
- July775 alerts
- Busiest day
- July 17, 201992 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
15 of 51 tornado warnings covering South Dakota in 2019 had a tornado report inside them; 19 of 28 tornado reports fell inside a warning, on average 11 minutes after it went out.
South Dakota, 2019
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 51 | 15 | 71% | 28 | 68% | 11 min |
| Severe thunderstorm warnings | 635 | 428 | 33% | 806 | 87% | 22 min |
| Flash flood warnings | 48 | 28 | 42% | 46 | 83% | 84 min |
Each office's whole area, 2019
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Aberdeen, SD: tornado warnings | 5 | 2 | 60% | 8 | 38% | 10 min |
| NWS Aberdeen, SD: severe thunderstorm warnings | 199 | 126 | 37% | 198 | 86% | 18 min |
| NWS Aberdeen, SD: flash flood warnings | 3 | 1 | 67% | 2 | 100% | 8 min |
| NWS Sioux Falls, SD: tornado warnings | 37 | 10 | 73% | 26 | 50% | 7 min |
| NWS Sioux Falls, SD: severe thunderstorm warnings | 172 | 107 | 38% | 251 | 88% | 18 min |
| NWS Sioux Falls, SD: flash flood warnings | 32 | 19 | 41% | 26 | 81% | 73 min |
| NWS Rapid City, SD: tornado warnings | 24 | 7 | 71% | 13 | 77% | 11 min |
| NWS Rapid City, SD: severe thunderstorm warnings | 444 | 289 | 35% | 588 | 87% | 24 min |
| NWS Rapid City, SD: flash flood warnings | 24 | 12 | 50% | 28 | 86% | 94 min |
An office's figures cover every county it serves, including across state lines.
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 alerts
2,541 alerts are too many to list on one page. Narrow it to a product above, to a month in the chart, or to a county.
By product
Every kind of product issued here, grouped by hazard. Each opens the same place narrowed to that product.
By county
Every county with at least one alert. A county page lists each alert that covered it.
- Pennington County347
- Lawrence County310
- Meade County294
- Custer County270
- Minnehaha County227
- Fall River County218
- Oglala Lakota County208
- Butte County206
- Jackson County197
- Bennett County175
- Haakon County174
- Moody County172
- Todd County171
- Charles Mix County165
- Lyman County165
- Tripp County165
- Perkins County163
- Lincoln County156
- Davison County155
- Ziebach County154
- Codington County151
- Hutchinson County151
- Mellette County151
- Gregory County150
- Brookings County149
- Brown County149
- McCook County149
- Harding County149
- Spink County148
- Hughes County147
- Hanson County147
- Hand County146
- Douglas County145
- Miner County144
- Corson County142
- Stanley County142
- Turner County141
- Jones County141
- Sanborn County140
- Edmunds County139
26 more counties
- Brule County139
- Hyde County138
- Faulk County137
- Roberts County136
- Hamlin County135
- Lake County134
- Beadle County134
- Aurora County133
- Union County132
- Day County131
- Marshall County131
- Deuel County129
- Campbell County129
- Dewey County129
- McPherson County129
- Sully County129
- Walworth County126
- Grant County125
- Kingsbury County124
- Potter County124
- Jerauld County123
- Clark County121
- Bon Homme County120
- Buffalo County119
- Clay County107
- Yankton County106
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordThe radar archive20182020
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.