(CNN)A very dry week with well-above average temperatures has worsened an already severe drought in the Western US, according to the US Drought Monitor.
New data shows the entirety of four states are under drought conditions -- California, Oregon, Utah and Nevada. Overall, drought is being experienced in 88% of the Western US as of this week. Scientists say persistent drought conditions in this region are being exacerbated by manmade climate change.
In addition to the critical water shortages this year's drought has caused, forecasters have raised concerns that the continued dry conditions will cause a particularly intense wildfire season. As of Thursday the Storm Prediction Center's fire weather outlook was classified as "critical" or "extreme" across parts of Wyoming, Utah, Colorado and Arizona.
"Warmer than normal temperatures dominated from California to the Dakotas with departures of 9-12 degrees above normal and even higher in the northern Plains," scientists with the US Drought Monitor wrote on Thursday. Areas of the South and southern Plains saw some improvement which was aided by rain and cooler temperatures.
"Exceptional drought" conditions, the most severe category, cover more than 26% of the West and nearly a tenth of the contiguous United States. Around half of the country is in abnormally dry conditions or worse, affecting an estimated 143 million people.
California's conditions worsened, with exceptional drought now covering a third of the state, up 7% from last week. The area of exceptional drought also grew in Utah and Colorado.
The Drought Monitor had predicted dry conditions would persist or expand in the US West in June.