The cover of Weather and a photo of Maureen on her wedding day with the text: Maureen Sweeney. How her weather observations changed the course of WW2

The 21-year-old Post Office worker who helped the D-Day landings

6 June 2021

May’s issue of Weather contains a fascinating ‘Weather in my Life’ interview with Mrs Maureen Sweeney. Maureen played a small but no less significant role in the success of D-Day (6 June 1944) and changed the course of World War II.

Maureen is now a much-loved mum, grandmother, great-grandmother, and great-great-grandmother, but 77 years ago it was her weather observations that directly contributed to the D-Day landings. Firstly, she informed the weather forecast that postponed D-Day, and then later the forecast that identified a window of opportunity for the Allied Forces.

Maureen was a sub-postmistress at Blacksod, a remote area of coastal County Mayo in the far west of Ireland. Her role included the taking and sending of meteorological observations from the weather station at Blacksod Post Office. Whilst the Republic of Ireland was neutral in WW2, it did allow the sharing of weather observations with Britain. Unaware of the importance of her readings and bound by the Official Secrets Act, it was another decade before Maureen realised that it was her readings, in particular the one she took at 01:00h on 3 June 1944 (on the morning of her 21st birthday!) that first alerted the Allies to the approaching storm that delayed D-Day.

For the Allied invasion to have had any chance of success, General Eisenhower – Supreme Commander of the Allied Forces - needed a full moon, a low tide, little cloud cover, light winds, and low seas. The low tide was necessary to allow soldiers to see, avoid, and disarm the mined obstacles. During June 1944, a full moon and low tide coincided on 5, 6 and 7 June. The invasion of France had been scheduled for June 5, 1944, but Maureen’s data threw Eisenhower’s meticulous strategy into chaos.

The team of meteorologists working on the invasion plans had to rely mainly on surface observations from military and civilian weather observers in Britain and Western Europe and a few military observers at sea. It was these observations that led one of Eisenhower’s chief meteorologists, Group Captain James Stagg, to postpone the invasion and deduce that there could be a break in the weather on 6 June.

That forecast was a pivotal moment in world history. If the forecast was wrong, the lives of thousands of men and massive amounts of equipment would be lost. If the unsettled weather forecast for 5 June had not happened, and the weather had been good, the Germans might have spied the massive build-up of forces along the coast of southern England.

To read more about Maureen’s Life in Weather, visit:

To read more about the D-Day forecast on MetMatters click this link.