How the forecast on D-Day changed the course of history

Meteorologist Sarah Spivey reflects on the 79th anniversary of WWII’s key battle

SAN ANTONIO – Imagine the pressure of having to accurately forecast the weather with countless lives and the fate of the free world at stake. That’s exactly what a team of British and American meteorologists was tasked to do 79 years ago for the battle of D-Day.

After months of planning, conditions had to be perfect for the invasion of Normandy. First, a full moon and low tide were necessary to expose Nazi defenses. This part was easy to forecast. However, given only a three-day window where astronomical conditions were right — June 5 through 7 — the weather also had to cooperate. Clear skies and calm winds and seas were vital. Otherwise, soldiers would be bogged down, planes would be off-target and ships would overturn.

Meteorology was still in its infancy in the '40s and any forecast more than 24 hours out was as good as a guess. The supreme commander of the Allied Forces, Dwight D. Eisenhower, originally chose June 5 as D-Day and consulted the team of Allied meteorologists. Having been told a storm would arrive, Eisenhower reluctantly canceled D-Day.

However, meteorologists believed there would be a small window of opportunity - June 6th - where the weather would be favorable for the invasions. On the other side of the line, German meteorologists believed that storms would persist for two weeks. In fact, many Nazis left their posts, believing that the Allies would not try again until July or August.

Eisenhower trusted his meteorologists and took the Germans off guard on the morning of June 6. At first, it was quite cloudy but the skies cleared and the Allies won the battle.

More than 4,000 brave Allied men died on the beaches of Normandy 79 years ago. Without their sacrifice, history could have made a bad turn. It’s also fascinating to think about how the forecast and the efforts of meteorologists played a key role in one of the most significant battles of WWII.

About the Author:

Sarah Spivey is a San Antonio native who grew up watching KSAT. She has been a proud member of the KSAT Weather Authority Team since 2017. Sarah is a Clark High School and Texas A&M University graduate. She previously worked at KTEN News. When Sarah is not busy forecasting, she enjoys hanging out with her husband and cat, and playing music.