Drought in Pennsylvania, May 1 to 31, 1999

Unseasonably dry weather returned to Eastern Pennsylvania during the month of May, especially in Berks, Carbon and Montgomery Counties (where only about 50 percent of normal rainfall fell). All counties received below normal precipitation. The closest to normal was the county weighted monthly average for Philadelphia of 3.9 inches (only .3 of an inch below normal). The heavy precipitation that fell on the 24th was confined to locations in and around Philadelphia. On a county weighted average, monthly rainfall totals ranged from 2.1 inches in Berks and Montgomery Counties to 3.9 inches in Philadelphia County. Streamflow rates remained below normal and averaged about 50 to 80 percent of normal. In the Lehigh River Basin stream flows were near or at record lows for the observation days. Ground water levels also declined except at a few sites in Bucks County. By the end of the month soil moisture levels were rated as either short or very short on one third of the farms in the state. Pasture growth was slow because of the dry conditions. Ground water levels did not recover to normal levels this spring. A well in Chester County Pennsylvania reached drought emergency levels. This is one of the aquifers that feed streams in northern Delaware. A drought watch did remain in effect for the Commonwealth of Pennsylvania.