None of the state was in that category a week ago.
Another 18 percent of the state is rated in severe drought, and 31 percent is in moderate drought.
The areas of extreme and severe drought are in north central south Dakota.
Drought conditions are harming crops and also have prompted many ranchers to sell off cattle.
Gov.
Dennis Daugaard last week issued an emergency declaration easing hay and transportation restrictions.
Rain and hail fell over parts of South Dakota Wednesday and early Thursday.
Storms caused extensive damage to a senior living facility in Castlewood, about 15 miles southeast of Watertown.
KELO-TVreports the Castlewood Assisted Living facility was evacuated when hail and strong winds moved through the area Wednesday night.
The storm temporarily knocked out power in the area.