WASHINGTON - The first English-speaking settlers in the New World had the bad luck to arrive just as the worst drought in 800 years began, bringing starvation, thirst, and death to Roanoke Island and Jamestown, according to a researcher at the College of William and Mary. A study of tree rings from ancient bald cypress trees gives an explanation for some of the hardships suffered at the settlements in North Carolina and Virginia, said Dennis B. Blanton, one of the authors of a study being published today in the journal Science. ''The English could not have found a worse time to found their settlements in the New World,'' said Blanton, an arch eologist at the College of William and Mary. ''There were other factors, but the drought clearly contributed to their major problems,'' he said.

Blanton teamed with tree ring specialists from the University of Arkansas to research the effect that weather may have had on the early settlements in the North Carolina and Virginia Tidewater area. Matthew D. Therrell of the University of Arkansas said his group could gather hints of weather conditions by measuring the width of tree rings from the trunk of the bald cypress, which can live for 1,000 years or more. They found that the rings were much smaller than average during the years of the Roanoke Island, N.C., settlement, 1587 to 1589, and in 1606 to 1612, the early years of the Jamestown, Va., settlement. ''Our estimate for drought during that period is that there was a very severe one,'' Therrell said. He said the years 1587 to 1589 marked the most extreme drought of any comparable period in the entire 800 years of the tree-ring record. It was during this period that the people of Roanoke, including Virginia Dare, the first English child born in America, disappeared.

Jamestown was founded in 1607, in the midst of the driest seven-year period in 770 years, Therrell said. Only 38 of the 104 original settlers survived the first year, and 4,800 of 6,000 people who lived there died between 1607 and 1625. Warren M. Billings, a specialist on the early English settlement of America, said the new tree ring study ''fills in some bits of the story that we didn't have,'' adding that drought was not the only reason that Roanoke failed and Jamestown residents suffered. The Roanoke Island settlement came to be known as the ''Lost Colony'' because its 120 residents disappeared after 1587. A ship that left them in America went back to England for supplies. The English-Spanish war intervened and by the time the ship returned to America in 1590, the Roanoke colony had been abandoned. The only trace was a tree carving of the word ''Croatoan,'' the name of a friendly tribe of Native Americans living nearby.