Western South Dakota is one of those classic drought cases. It was extraordinarily wet there during the 1990s, well above the long term mean. Of the 10 wettest years in a century of records in northwest South Dakota, four came during the 1990s. An astonishing six years during the 1990s were greater than one standard deviation wetter than the long term mean in the southwest South Dakota climate division.
Andrea Cook at the Rapid City Journal gets points for trying to explain this to folks:
South Dakota benefited from relatively wet periods through most of the 1990s and in 2001, Todey said.
But her story reflects what seems to be an inevitable mistake in thinking about drought in this country (not her mistake, but the mistake of the people she’s talking to). Variation around the mean is normal. When we’re on the wet side of the mean – even way on the wet side of the mean – agriculturalists in the United States treat it as “normal,” expanding herds, planting, etc. (See my previous discussion of the fact that we don’t really have a word for the opposite of “drought”.) When we slip to the dry side of the mean, that’s a “drought”. There’s no question that western South Dakota has been on the dry side of the mean for the last five years. But within the ups and downs, the Standardized Precipitation Index for the region shows “near normal” conditions.