flash drought
n. A drought that develops abnormally quickly.
Droughts typically develop slowly, so a "flash drought" happens within weeks rather than months, said Jim Angel, the Illinois state climatologist.
—Karen Chen, “Cool, rainy summer days just a memory as 'flash drought' hits Illinois,” Chicago Tribune, September 13, 2013
A recent spate of hot, dry weather has brought about a "flash drought" in parts of the U.S. Midwest, according to a weekly government report Thursday….
"Above-normal temperatures and rapidly deteriorating soil moisture conditions have resulted in what appears to be a late-season flash drought," said Anthony Artusa, who wrote the report and is a meteorologist with the National Oceanic and Atmospheric Administration.
—Ian Berry, “'Flash Drought' Hits Parts of Midwest,” The Wall Street Journal, August 29, 2013
2001 (earliest)
Southwest Nebraska has experienced rapid drying conditions the past two months and is abnormally dry, said Mark Svoboda, a specialist with the National Drought Mitigation Center located at the University of Nebraska-Lincoln.

"We kind of liken this to a flash drought," Svoboda told the Climate Assessment Response Committee, which was set up to monitor drought conditions.
—Kevin O'Hanlon, “Danger of drought's return looms in parts of Nebraska,” The Associated Press, July 19, 2001