Weather alerts in South Dakota, 2015
1,721 weather alerts in 2015, 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 2015. Tap one for its archive.
- Alerts
- 1,721
- Warnings
- 839
- Watches
- 125
- Advisories
- 202
- Busiest month
- June477 alerts
- Busiest day
- August 9, 201565 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
19 of 52 tornado warnings covering South Dakota in 2015 had a tornado report inside them; 23 of 32 tornado reports fell inside a warning, on average 14 minutes after it went out.
South Dakota, 2015
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 52 | 19 | 63% | 32 | 72% | 14 min |
| Severe thunderstorm warnings | 582 | 439 | 25% | 822 | 88% | 24 min |
| Flash flood warnings | 36 | 22 | 39% | 32 | 94% | 53 min |
Each office's whole area, 2015
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Rapid City, SD: tornado warnings | 16 | 5 | 69% | 11 | 64% | 14 min |
| NWS Rapid City, SD: severe thunderstorm warnings | 307 | 238 | 22% | 460 | 88% | 26 min |
| NWS Rapid City, SD: flash flood warnings | 18 | 9 | 50% | 13 | 92% | 99 min |
| NWS Aberdeen, SD: tornado warnings | 19 | 4 | 79% | 5 | 80% | 9 min |
| NWS Aberdeen, SD: severe thunderstorm warnings | 205 | 150 | 27% | 308 | 85% | 22 min |
| NWS Aberdeen, SD: flash flood warnings | 9 | 6 | 33% | 10 | 100% | 68 min |
| NWS Sioux Falls, SD: tornado warnings | 30 | 13 | 57% | 25 | 68% | 14 min |
| NWS Sioux Falls, SD: severe thunderstorm warnings | 175 | 123 | 30% | 220 | 86% | 20 min |
| NWS Sioux Falls, SD: flash flood warnings | 19 | 13 | 32% | 19 | 95% | 37 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
1,721 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 County235
- Meade County199
- Lawrence County170
- Custer County169
- Brown County147
- Jackson County136
- Butte County130
- Haakon County126
- Codington County125
- Minnehaha County123
- Spink County122
- Lincoln County120
- Lyman County119
- Lake County117
- Grant County117
- Day County116
- Roberts County116
- Fall River County115
- Tripp County114
- Moody County113
- McPherson County113
- Bennett County113
- Kingsbury County112
- Sanborn County112
- Edmunds County112
- Hamlin County112
- Hand County112
- Mellette County112
- Beadle County111
- Brookings County111
- Clark County111
- Todd County111
- Hutchinson County110
- McCook County110
- Turner County110
- Deuel County110
- Faulk County110
- Marshall County110
- Miner County108
- Davison County107
26 more counties
- Union County107
- Harding County107
- Perkins County107
- Charles Mix County106
- Ziebach County104
- Aurora County103
- Jones County103
- Jerauld County101
- Corson County101
- Dewey County101
- Hanson County100
- Hyde County100
- Brule County99
- Clay County99
- Douglas County99
- Potter County99
- Stanley County99
- Walworth County98
- Campbell County97
- Yankton County96
- Gregory County95
- Hughes County93
- Buffalo County92
- Sully County92
- Bon Homme County88
- Oglala Lakota County81
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordThe radar archive20142016
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.