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Palmer Index May through September, 1999:

Flooding in the Central Valley of California: - Long Term Palmer Drought Severity Index for the summer of 1999. Dry areas are red, moist areas are green. Drought gripped most of the eastern United States with extreme drought persisting through the Ohio Valley into early fall. Note that the western U.S. also develops drought conditions by late summer.

Department of Atmospheric Sciences Severe and Hazardous Weather at Department of Atmospheric Sciences University of Illinois