Maureen Flavin Sweeney, Whose Weather Report Delayed D-Day, Dies at 100

On certain rare occasions, ordinary people in the midst of an average day have changed history.

In 1947, Muhammad edh-Dhib, a young Bedouin shepherd looking for a sheep gone astray, discovered a hidden cave that contained the Dead Sea Scrolls, the earliest known version of most of the Hebrew Bible. Making his rounds one night in 1972, Frank Wills, a Washington, D.C., security guard, noticed a piece of tape holding a lock open in a building where he worked — and as a result he exposed the Watergate break-in, ultimately leading to the resignation of President Richard M. Nixon.

But neither of them shaped as many lives as directly as Maureen Flavin, a postal clerk on a remote stretch of the northwest Irish coast who, in 1944, on her 21st birthday, helped determine the outcome of the Second World War.

She died on Dec. 17 in a nursing home in Belmullet, Ireland, near the post office where she used to work, her grandson Fergus Sweeney said. She was 100.

The events that led Ms. Flavin to her unforeseeable moment of global consequence began in 1942 when she saw an ad for a job in the post office of the coastal village of Blacksod Point.