National Climatic Data Center, 13 September 2002

As noted by the Wyoming state climatologist (Jan Curtis),

Based on some measures, the current drought is not as severe as the droughts of the 1930s and 1950s.

The most recent statewide drought that began in the spring of 2000 over
Wyoming is considered by many to be the most severe in their collective
memory.  However, some old timers have indicated that they remember streams
drying up in the 1930's and 1950's.  According to instrument records since
1895, there have been only seven multi-year (3 years or longer) statewide
droughts.  Based on deficit precipitation totals, they are ranked as
follows:

Drought    Deficit (from annual precipitation)   Drought Deficit
1952-1956    94%                               1987-1990    61%
1958-1964    77%                               1999-200X    46% (thru 2001)
1900-1903    72%                               1974-1977    41%
1931-1936    61%

The worst multi-year droughts by climate divisions are:

                annual %                                    annual %
Greatest Total Deficit (per drought)   Greatest Average Annual Deficit (per year of drought)
CD1:   1931-1936  (-116)               1998-200X  (-21) (thru 2001) Yellowstone
CD2:   1987-1992  (-106)               1958-1962  (-21)  Snake/Salt
CD3:   1900-1903  (-120)               1988-1990  (-34)  Bear/Green
CD4:   1948-1956  (-211)               1933-1936  (-25)  Big Horn
CD5:   1959-1961  (-79)                1959-1961  (-26)  Powder-Tongue
CD6:   1930-1940  (-180)               1952-1954  (-21)  Belle Fourche
CD7:   1958-1961  (-96)                1958-1961  (-24)  Cheyenne
CD8:   1974-1980  (-110)               1952-1954  (-22)  Lower N. Platte
CD9:   1979-1990  (-229)               1999-200X  (-30)  (thru 2001) Wind River
CD10:  1952-1956  (-114)               1952-1956  (-23)  Upper N. Platte