Dewey County Natural Disasters and Weather Extremes
The chance of earthquake damage in Dewey County is about the same as South Dakota average and is much lower than the national average. The risk of tornado damage in Dewey County is much lower than South Dakota average and is much lower than the national average.
Earthquake Index, #52
| Dewey County | 0.01 |
| South Dakota | 0.05 |
| U.S. | 1.81 |
The earthquake index value is calculated based on historical earthquake events data using USA.com algorithms. It is an indicator of the earthquake level in a region. A higher earthquake index value means a higher chance of an earthquake.
Volcano Index, #1
| Dewey County | 0.0000 |
| South Dakota | 0.0000 |
| U.S. | 0.0023 |
The volcano index value is calculated based on the currently known volcanoes using USA.com algorithms. It is an indicator of the possibility of a region being affected by a possible volcano eruption. A higher volcano index value means a higher chance of being affected.
Tornado Index, #55
| Dewey County | 36.52 |
| South Dakota | 114.73 |
| U.S. | 136.45 |
The tornado index value is calculated based on historical tornado events data using USA.com algorithms. It is an indicator of the tornado level in a region. A higher tornado index value means a higher chance of tornado events.
Other Weather Extremes Events
A total of 4,302 other weather extremes events within 50 miles of Dewey County were recorded from 1950 to 2010. The following is a break down of these events:
| Type | Count | Type | Count | Type | Count | Type | Count | Type | Count |
| Avalanche: | 0 | Blizzard: | 0 | Cold: | 0 | Dense Fog: | 0 | Drought: | 0 |
| Dust Storm: | 0 | Flood: | 148 | Hail: | 2,484 | Heat: | 0 | Heavy Snow: | 0 |
| High Surf: | 0 | Hurricane: | 0 | Ice Storm: | 0 | Landslide: | 0 | Strong Wind: | 0 |
| Thunderstorm Winds: | 1,593 | Tropical Storm: | 0 | Wildfire: | 18 | Winter Storm: | 0 | Winter Weather: | 0 |
| Other: | 59 | ||||||||
Volcanos Nearby
No volcano is found in or near Dewey County.
Historical Earthquake Events
No historical earthquake events that had recorded magnitudes of 3.5 or above found in or near Dewey County.
No historical earthquake events found in or near Dewey County.
Historical Tornado Events
A total of 13 historical tornado events that had recorded magnitude of 2 or above found in or near Dewey County.
| Distance (miles) | Date | Magnitude | Start Lat/Log | End Lat/Log | Length | Width | Fatalities | Injuries | Property Damage | Crop Damage | Affected County |
| 8.2 | 1964-06-08 | 2 | 45°05'N / 100°42'W | 45°09'N / 100°41'W | 3.80 Miles | 33 Yards | 0 | 1 | 0K | 0 | Dewey |
| 16.8 | 1955-04-19 | 2 | 45°03'N / 101°10'W | 0 | 0 | 3K | 0 | Dewey | |||
| 18.2 | 1953-06-02 | 2 | 45°00'N / 101°14'W | 45°01'N / 101°06'W | 5.90 Miles | 33 Yards | 0 | 0 | 25K | 0 | Dewey |
| 23.7 | 2010-06-16 | 2 | 45°03'N / 101°19'W | 45°03'N / 101°19'W | 0 | 0 | 0K | 0K | Dewey | ||
| Brief Description: EVENT NARRATIVE: A tornado touched down briefly on a farm six miles northwest of Eagle Butte. Two homes suffered severe structural damage with several pole barns destroyed. Also several pieces of agricultural equipment were damaged or destroyed. A horse was severely injured and had to be put down. Wind speeds were estimated between 120 and 125 mph. EPISODE NARRATIVE: Several supercell thunderstorms brought very heavy rains of 4 to 7 inches, hail up to golfball size, winds to over 100 mph, along with a tornado to parts of north central South Dakota. Dewey county was the most affected by the storms. | |||||||||||
| 27.1 | 1970-07-18 | 2 | 45°06'N / 100°18'W | 0 | 0 | 0K | 0 | Potter | |||
| 37.2 | 2010-06-16 | 2 | 45°02'N / 101°36'W | 45°03'N / 101°36'W | 1.00 Mile | 450 Yards | 0 | 2 | 750K | 0K | Ziebach |
| Brief Description: EVENT NARRATIVE: Another tornado touched down just south of Dupree and moved along the west side of town. It tore the roof off the community center, damaged a house and garage, crumpled large grain bins, and tossed several mobile homes. One person was injured when a mobile home was blown into the car in which he had taken cover and another person received minor injuries. EPISODE NARRATIVE: A tornadic thunderstorm developed over central Ziebach County and slowly moved northeastward toward Red Elm and Dupree. The storm lingered and regenerated over the Dupree area for more than three hours; producing large hail, wind gusts near 100 mph, sixteen tornadoes, and torrential rainfall that caused widespread flooding. Significant damage occurred in Dupree, where several mobile homes were blown over, roofs were damaged, and trees were downed. Two people were injured in Dupree. | |||||||||||
| 39.1 | 1955-04-19 | 2 | 45°01'N / 100°07'W | 45°16'N / 99°59'W | 18.20 Miles | 27 Yards | 0 | 0 | 3K | 0 | Potter |
| 42.5 | 1983-06-21 | 3 | 45°24'N / 101°43'W | 45°26'N / 101°34'W | 6.00 Miles | 300 Yards | 0 | 0 | 250K | 0 | Ziebach |
| 43.4 | 1968-06-20 | 3 | 45°32'N / 100°13'W | 45°30'N / 100°02'W | 8.80 Miles | 200 Yards | 0 | 0 | 0K | 0 | Walworth |
| 44.9 | 1971-10-01 | 2 | 44°43'N / 100°10'W | 0.50 Mile | 300 Yards | 0 | 0 | 25K | 0 | Sully | |
| 45.4 | 1969-07-07 | 2 | 45°48'N / 101°00'W | 0 | 0 | 0K | 0 | Lawrence | |||
| 46.1 | 1953-05-29 | 2 | 45°49'N / 100°49'W | 0.50 Mile | 33 Yards | 0 | 2 | 250K | 0 | Corson | |
| 46.5 | 1968-06-20 | 3 | 45°30'N / 100°02'W | 0 | 0 | 0K | 0 | Walworth | |||
* The information on this page is based on the global volcano database, the U.S. earthquake database of 1638-1985, and the U.S. Tornado and Weather Extremes database of 1950-2010.