Four Standout Years

The following table indicates the difference in rainfall distribution (warm season vs. cool season) when the last four years are compared to the long-term averages. Despite dry summers (especially dry in the west), annual rainfall has been at or above normal due to exceptionally wet cool seasons (again, especially in the west).

The circle represents the annual rainfall during the given period. The area of the circle is proportional to the amount of rain. Rain during the cool season (October through March) is in blue; red indicates warm season (April through September) rainfall.

The most noticable differences occur in climate divisions 1, 4, 7, 8 and 9, in western and southern Oklahoma. In these divisions, cool season rainall was dramatically greater during the last four years than at any time in the last 100 years.

Climate divisions 1, 2, 4, and 8 observed more cool-season rainfall during the last four years (ending March 2001) than during any four-year period in recorded history (CD 7 observed the 2nd largest such total).


Oklahoma: Statewide Average
Long-Term Average Last Four Years
Average Annual Rain: 33.93"
During Cool Season: 12.49"
During Warm Season: 21.44"
Cool Season Share: 37 %		 Average Annual Rain: 39.92"
During Cool Season: 17.87"
During Warm Season: 22.05"
Cool Season Share: 45 %
 
Climate Division One: Panhandle
Long-Term Average Last Four Years
Average Annual Rain: 19.85"
During Cool Season: 5.23"
Warm-season Rain: 14.62"
Cool Season Share: 26 % 		Average Annual Rain: 24.60"
During Cool Season: 9.70"
During Warm Season: 14.90"
Cool Season Share: 39 %
 
Climate Division Two: North Central
Long-Term Average Last Four Years
Average Annual Rain: 28.80"
During Cool Season: 9.06"
During Warm Season: 19.74"
Cool Season Share: 31 % 		Average Annual Rain: 39.08"
During Cool Season: 16.75"
During Warm Season: 22.33"
Cool Season Share: 43 %
 
Climate Division Three: Northeast
Long-Term Average Last Four Years
Average Annual Rain: 39.94"
During Cool Season: 14.81"
During Warm Season: 25.13"
Cool Season Share: 37 % 		Average Annual Rain: 47.80"
During Cool Season: 18.21"
During Warm Season: 29.59"
Cool Season Share: 38 %
 
Climate Division Four: West Central
Long-Term Average Last Four Years
Average Annual Rain: 26.37"
During Cool Season: 8.27"
During Warm Season: 18.10"
Cool Season Share: 31 % 		Average Annual Rain: 30.65"
During Cool Season: 13.81"
During Warm Season: 16.84"
Cool Season Share: 45 %
 
Climate Division Five: Central
Long-Term Average Last Four Years
Average Annual Rain: 34.42"
During Cool Season: 12.04"
During Warm Season: 22.28"
Cool Season Share: 35 % 		Average Annual Rain: 40.74"
During Cool Season: 17.86"
During Warm Season: 22.88"
Cool Season Share: 44 %
 
Climate Division Six: East Central
Long-Term Average Last Four Years
Average Annual Rain: 43.21"
During Cool Season: 17.69"
During Warm Season: 25.52"
Cool Season Share: 41 % 		Average Annual Rain: 50.75"
During Cool Season: 22.78"
During Warm Season: 27.97"
Cool Season Share: 45 %
 
Climate Division Seven: Southwest
Long-Term Average Last Four Years
Average Annual Rain: 27.84"
During Cool Season: 9.40"
During Warm Season: 18.44"
Cool Season Share: 34 % 		Average Annual Rain: 31.48"
During Cool Season: 14.86"
During Warm Season: 16.62"
Cool Season Share: 47 %
 
Climate Division Eight: South Central
Long-Term Average Last Four Years
Average Annual Rain: 37.48"
During Cool Season: 15.01"
During Warm Season: 22.47"
Cool Season Share: 40 % 		Average Annual Rain: 41.08"
During Cool Season: 20.93"
During Warm Season: 20.15"
Cool Season Share: 51 %
 
Climate Division Nine: Southeast
Long-Term Average Last Four Years
Average Annual Rain: 48.12"
During Cool Season: 21.77"
During Warm Season: 26.35"
Cool Season Share: 45 % 		Average Annual Rain: 52.28"
During Cool Season: 26.69"
During Warm Season: 25.89"
Cool Season Share: 51 %