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.

CRYSTAL, N.D. — Drought is rearing its ugly head across much of Agweek Country.
The 2016 crop season in Crystal and much of the rest of northeast North Dakota was ravaged by storms that brought hail, high winds and heavy and frequent precipitation.
The difficult growing season also created extra stress and frustration for farmers and other agriculturalists.
But all the 2016 precipitation left many fields with plentiful subsoil moisture, which will help crops withstand hot, windy stretches this growing season.
Having subsoil moisture doesn’t eliminate the need for summer rains, but it provides some cushion.
Diverse crops Farmers in the Crystal area grow many crops.
Corn, soybeans, wheat, sugar beets, potatoes and dry edible beans are most common; other crops, including canola and sunflowers are raised, too.
Though Crystal, population about 150, struggled in 2016, the community enjoyed a wave of new construction in 2010-11.
Though the subsoil moisture will help with that, rain will be needed, too.
Ganssle says that applies this growing season in his area.

Mixed in with the rain was marble- to golfball-sized hail early Saturday morning, with reports of baseball-size hail north and west of Plainview.
It hit Dimmitt about 7:20 p.m., and at 10 p.m. Friday the National Weather Service on twitter reported that Highway 86 and US 385 were closed in all directions outside of Dimmitt due to flooding.
The storm moved into Plainview about midnight Saturday, bringing with it marble- to golfball-sized hail and heavy rain.
Heaviest measured rainfall was from the Mesonet site 2 miles northeast of Dimmitt with 1.87 inches.
The Plainview Water Treatment Plant reported 0.98 inch, Plainview Herald 0.63 inch and Plainview’s Mesonet site 0.37 inch.
That along with a dryline south of the front and expected weak upper support within a modest west-southwest flow aloft should spur scattered storm development Sunday afternoon and evening.
Just 0.01 percent of Texas is in severe drought, with 1.7 percent in moderate drought, down from almost 3 percent a week ago.
Those dry areas are in northeast Texas.
Currently 13.55 percent of Texas is abnormally dry but not yet in drought.
At this point in 2016, Plainview had just 0.84 inch of moisture.

A new comprehensive study of Australian natural hazards paints a picture of increasing heatwaves and extreme bushfires as this century progresses, but with much more uncertainty about the future of storms and rainfall.
Published in a special issue of the international journal Climatic Change, the study documents the historical record and projected change of seven natural hazards in Australia: flood; storms (including wind and hail); coastal extremes; drought; heatwave; bushfire; and frost.
"Temperature-related hazards, particularly heatwaves and bushfires, are increasing, and projections show a high level of agreement that we will continue to see these hazards become more extreme into the 21st century," says special issue editor Associate Professor Seth Westra, Head of the Intelligent Water Decisions group at the University of Adelaide.
"The study documents our current understanding of the relationship between historical and possible future climatic change with the frequency and severity of Australian natural hazards," says Associate Professor Westra.
"These hazards cause multiple impacts on humans and the environment and collectively account for 93% of Australian insured losses, and that does not even include drought losses.
The biggest risk from climate change is if we continue to plan as though there will be no change.
One thing is certain: our environment will continue to change."
• Heatwaves are Australia’s most deadly natural hazard, causing 55% of all natural disaster related deaths and increasing trends in heatwave intensity, frequency and duration are projected to continue throughout the 21st century.
• The costs of flooding have increased significantly in recent decades, but factors behind this increase include changes in reporting mechanisms, population, land-use, infrastructure as well as extreme rainfall events.
The physical size of floods has either not changed at all, or even decreased in many parts of the country.