Total precipitation during the 1991 water year was about 123 percent of normal in western Washington and about 95 percent of normal in eastern Washington. The total precipitation for the water year ranged between about 84 and 139 percent of normal throughout the State. Precipitation during September was the farthest below normal for a month when the monthly total was about 11 percent of normal in western Washington and about 12 percent of normal in eastern Washington. Monthly precipitation was the farthest above normal during November in western Washington, and during June in eastern Washington, when monthly totals were about 218 and 190 percent of normal, respectively.

Rainfall in western Washington was less than 75 percent of normal during the months of July and September. It was near normal during December, January, March, May, and June, and was more than 125 percent of normal during October, November, February, April, and August.

In eastern Washington, precipitation was less than 75 percent of normal during the months of November, December, January, February, and September. It was near normal during April, July, and August, and was more than 125 percent of normal during October, March, May, and June.

The annual mean runoff was near or above normal in western Washington and northeastern Washington, and near or below normal in southeastern Washington during the 1991 water year.

During the 1991 water year, three significant flood events occurred in Washington. The timing of the flood events was very similar to those in the 1990 water year. Major flooding occurred November 10, 11 in the Skagit and Nooksack River basins and northward into Canada. Peak flows at gaging stations in these basins had recurrence intervals of up to 50 years. During November 24-26, widespread flooding occurred at many sites throughout northwestern Washington. Major flooding and damage were reported at many sites in the Puget sound area, particularly in the Nooksack, Skagit River, and Snohomish River basins. Record peak flows were recorded at many gaging stations with recurrence intervals at some sites of 100 years or greater. Less significant flood events occurred in the Puget Sound basin area on February 19 and on April 5 with recurrence intervals of 5 years or less. (A peak flow that has a recurrence interval of five years can be expected to be exceeded once in five years on the average.) Significant peak flows occurring in eastern Washington were mainly in the northern area and had recurrence intervals of less than 5 years.

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