Throughout much of the United States the Palmer Drought Severity
Index (also known as the Palmer Index) is used to assess drought
conditions. The Palmer Index is primarily a method of comparing
recent monthly precipitation with average or "normal"
conditions. Palmer Index values are scaled from +4 (extremely
moist) to -4 (extreme drought) with a value of zero (0) indicating
historic average conditions.
Depicted in the seven charts below is the 100-year record of
Palmer Index values for the seven climatic regions of the state.
Although the years are shown chronologically the Palmer Index
values for the months are not (i.e. month 1 is not necessarily
January, month 2 is not necessarily February, etc.). In other
words, for Climatic Division I, in the year 2000 there were
five months of moderate drought, three months of severe drought
and four months of extreme drought.
