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.
She got the job and learned that the remote post office also served as a weather station. Her duties included recording and transmitting weather data. She did that work diligently, though she did not even know where her weather reports were going.
In fact, they were part of the Allied war effort.
Ireland was neutral in World War II but quietly helped the Allies in several ways, including by sharing weather data with Britain. Ireland’s position on Europe’s northwestern edge gave it an early sense of weather heading toward the continent. Blacksod Point was just about the westernmost point of the coast.
Weather forecasting turned out to be an essential part of the Allies’ most famous gambit of the war — D-Day, the invasion aimed at gaining a foothold on the European mainland.
It took two years of meticulous planning. The American general Dwight D. Eisenhower, who led the assault, decided to send more than 160,000 troops, nearly 12,000 aircraft and nearly 7,000 sea vessels to invade a 50-mile stretch of beach along the Normandy region of the French coast.
The Allies settled on June 5, 1944, which promised a full moon, aiding visibility, and low tides, granting easier access to the beach.
A successful invasion would also depend on clear skies for the Allies’ aerial assault and calm seas for their landing. And the relatively primitive technology of the day — no satellites, no computer models — meant that the Allies would only have a few days’ warning about the weather.
By 1944, Ms. Flavin’s work orders had increased from on high: She and her colleagues now sent in weather reports not every six hours, but every hour of the day.
“You would only have one finished when it was time to do another,” she recalled in a documentary made by RTÉ, Ireland’s public broadcaster, in 2019.
On her birthday, June 3, she had a late-night shift: 12 a.m. to 4 a.m. Checking her barometer, she registered a rapid drop in pressure indicating a likelihood of approaching rain or stormy weather.
