Several factors, including La Niña events, have contributed to the expanded drought, meteorologists say. Conditions in the West may be setting up for a 'megadrought' by century's end, researchers warn.
In late July 2011 the US drought had a parched core centered in the southern Plains and stretched along much of the southern tier. About 30 percent of the continental US was experiencing drought at varying degrees of severity, and another 11 percent was considered abnormally dry.
This year it has overspread most of the country.
Sixty-three percent of the continental US is now drought-stricken, a figure that grows to 79 percent when abnormally dry areas are included, according to the latest figures from the National Drought Mitigation Center in Lincoln, Neb.
"It's kind of like the blob in the old Steve McQueen movie,” says Martin Hoerling, a research meteorologist at the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory.
Summer monsoons have brought some relief to the Southwest and up into the Rocky Mountain states. Early tropical storms also eased dryness along the Gulf of Mexico and into the southeastern corner of the country.
But forecasters are calling for the drought to expand its boundaries through the end of October to cover more of Michigan, Minnesota, and the Dakotas, while to the east drought is expected to move deeper into Pennsylvania and West Virginia.
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