Weather alerts in South Dakota, 2018
2,175 weather alerts in 2018, 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 2018. Tap one for its archive.
- Alerts
- 2,175
- Warnings
- 985
- Watches
- 100
- Advisories
- 233
- Busiest month
- June604 alerts
- Busiest day
- July 4, 201866 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
8 of 30 tornado warnings covering South Dakota in 2018 had a tornado report inside them; 10 of 22 tornado reports fell inside a warning, on average 14 minutes after it went out.
South Dakota, 2018
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 30 | 8 | 73% | 22 | 45% | 14 min |
| Severe thunderstorm warnings | 621 | 419 | 33% | 840 | 83% | 22 min |
| Flash flood warnings | 46 | 35 | 24% | 55 | 71% | 91 min |
Each office's whole area, 2018
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Sioux Falls, SD: tornado warnings | 12 | 3 | 75% | 10 | 40% | 9 min |
| NWS Sioux Falls, SD: severe thunderstorm warnings | 165 | 77 | 53% | 157 | 81% | 19 min |
| NWS Sioux Falls, SD: flash flood warnings | 43 | 31 | 28% | 66 | 82% | 104 min |
| NWS Aberdeen, SD: tornado warnings | 7 | 2 | 71% | 9 | 33% | 8 min |
| NWS Aberdeen, SD: severe thunderstorm warnings | 233 | 158 | 32% | 290 | 82% | 17 min |
| NWS Aberdeen, SD: flash flood warnings | 12 | 11 | 8% | 16 | 69% | 142 min |
| NWS Rapid City, SD: tornado warnings | 18 | 6 | 67% | 14 | 64% | 18 min |
| NWS Rapid City, SD: severe thunderstorm warnings | 376 | 273 | 27% | 586 | 84% | 24 min |
| NWS Rapid City, SD: flash flood warnings | 13 | 8 | 38% | 16 | 69% | 42 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
2,175 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.
| Product | Alerts |
|---|---|
| Severe storms | |
| Severe Thunderstorm Warning | 621 |
| Tornado Warning | 30 |
| Severe Thunderstorm Watch | 38 |
| Tornado Watch | 7 |
| Mesoscale Discussion | 175 |
| Special Weather Statement | 682 |
| Flooding | |
| Areal Flood Warning | 55 |
| Flash Flood Warning | 46 |
| River Flood Warning | 165 |
| Flash Flood Watch | 12 |
| Flood Watch | 3 |
| Areal Flood Advisory | 18 |
| Winter | |
| Blizzard Warning | 12 |
| Winter Storm Warning | 29 |
| Winter Storm Watch | 32 |
| Winter Weather Advisory | 85 |
| Heat | |
| Heat Advisory | 13 |
| Cold | |
| Freeze Warning | 7 |
| Wind Chill Warning | 2 |
| Freeze Watch | 2 |
| Frost Advisory | 8 |
| Wind Chill Advisory | 23 |
| Wind and dust | |
| High Wind Warning | 7 |
| High Wind Watch | 1 |
| Wind Advisory | 43 |
| Fire | |
| Red Flag Warning | 11 |
| Fire Weather Watch | 5 |
| Fog and smoke | |
| Dense Fog Advisory | 43 |
By county
Every county with at least one alert. A county page lists each alert that covered it.
- Pennington County265
- Meade County251
- Custer County214
- Lawrence County212
- Butte County196
- Perkins County176
- Corson County171
- Harding County169
- Dewey County154
- Oglala Lakota County154
- Hand County152
- Walworth County151
- Lyman County149
- Ziebach County148
- McPherson County146
- Todd County145
- Faulk County143
- Jackson County143
- Sully County141
- Edmunds County138
- Minnehaha County138
- Haakon County136
- Stanley County134
- Fall River County134
- Brown County133
- Campbell County133
- Union County133
- Hughes County132
- Potter County132
- Spink County131
- Bennett County130
- Jones County129
- Hyde County127
- Day County117
- Tripp County115
- Codington County114
- Grant County114
- Marshall County114
- Roberts County113
- Mellette County113
26 more counties
- Charles Mix County112
- Hutchinson County112
- Lincoln County112
- Turner County106
- Brookings County103
- Brule County101
- Moody County101
- Buffalo County99
- Deuel County98
- Clark County95
- Aurora County95
- Bon Homme County94
- Yankton County93
- Douglas County92
- Clay County91
- McCook County91
- Gregory County90
- Hamlin County89
- Hanson County89
- Davison County88
- Lake County83
- Miner County79
- Jerauld County78
- Sanborn County78
- Beadle County74
- Kingsbury County74
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordThe radar archive20172019
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.