Weather alerts in South Dakota, 2020
2,099 weather alerts in 2020, 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 2020. Tap one for its archive.
- Alerts
- 2,099
- Warnings
- 1,003
- Watches
- 117
- Advisories
- 240
- Busiest month
- July659 alerts
- Busiest day
- July 6, 202067 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
6 of 37 tornado warnings covering South Dakota in 2020 had a tornado report inside them; 7 of 29 tornado reports fell inside a warning, on average 15 minutes after it went out.
South Dakota, 2020
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 37 | 6 | 84% | 29 | 24% | 15 min |
| Severe thunderstorm warnings | 764 | 562 | 26% | 1,233 | 85% | 24 min |
| Flash flood warnings | 24 | 15 | 38% | 24 | 83% | 88 min |
Each office's whole area, 2020
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Sioux Falls, SD: tornado warnings | 18 | 2 | 89% | 4 | 50% | 17 min |
| NWS Sioux Falls, SD: severe thunderstorm warnings | 202 | 151 | 25% | 298 | 88% | 21 min |
| NWS Sioux Falls, SD: flash flood warnings | 13 | 9 | 31% | 17 | 71% | 67 min |
| NWS Rapid City, SD: tornado warnings | 11 | 2 | 82% | 11 | 27% | 18 min |
| NWS Rapid City, SD: severe thunderstorm warnings | 415 | 336 | 19% | 828 | 89% | 27 min |
| NWS Rapid City, SD: flash flood warnings | 10 | 7 | 30% | 11 | 91% | 88 min |
| NWS Aberdeen, SD: tornado warnings | 11 | 3 | 73% | 16 | 19% | 6 min |
| NWS Aberdeen, SD: severe thunderstorm warnings | 262 | 160 | 39% | 356 | 78% | 19 min |
| NWS Aberdeen, SD: flash flood warnings | 4 | 1 | 75% | 1 | 100% | 205 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
2,099 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 County325
- Meade County278
- Custer County212
- Lawrence County207
- Jackson County193
- Perkins County184
- Todd County179
- Haakon County174
- Butte County173
- Bennett County169
- Oglala Lakota County169
- Stanley County167
- Harding County160
- Brown County157
- Jones County153
- Ziebach County150
- Lyman County146
- Edmunds County145
- Dewey County142
- McPherson County142
- Hand County141
- Mellette County139
- Spink County139
- Faulk County138
- Sully County135
- Roberts County134
- Hughes County133
- Hyde County132
- Potter County131
- Charles Mix County131
- Tripp County128
- Fall River County126
- Codington County124
- Marshall County123
- Walworth County122
- Campbell County119
- Day County118
- Beadle County117
- Corson County116
- Brule County116
26 more counties
- Brookings County115
- Hamlin County115
- Douglas County115
- Union County114
- Grant County113
- Gregory County112
- Davison County111
- Buffalo County110
- Hutchinson County110
- Aurora County109
- Moody County107
- Clark County107
- Kingsbury County106
- Minnehaha County106
- Hanson County104
- Miner County104
- Clay County103
- Deuel County102
- Bon Homme County102
- Lincoln County101
- Lake County97
- McCook County97
- Sanborn County97
- Yankton County97
- Jerauld County96
- Turner County94
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordThe radar archive20192021
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.