Total precipitation during the 1987 water year was about 90 percent of normal in western Washington and about 80 percent of normal in eastern Washington. The total precipitation for the water year ranged between about 75 and 95 percent of normal throughout the State. Precipitation during September was the farthest below normal for a month. It was about 30 percent of normal in western Washington and about 10 percent of normal in eastern Washington. Monthly precipitation was the farthest above normal during November in western Washington, and during July in eastern Washington, when monthly totals exceeded 150 and 250 percent of normal, respectively.

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

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

The annual mean runoff in both western and eastern Washington during the 1987 water year was generally below normal.

Significant floodflows occurred in western Washington only once during the 1987 water year. During November 23-24, most streams of coastal and west-central Washington went above flood stage. Peak flows at gaging stations of coastal Washington had recurrence intervals generally ranging form 5 to 10 years. Peak flows at gaging stations in west-central Washington had recurrence intervals generally ranging from 5 to 20 years but locally exceeding 40 years. (A peak flow that has a recurrence interval of five years can be expected to be exceeded once in five years on the average.) The annual peak flows at most gaging stations in eastern Washington had recurrence intervals of one to two years.

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