This story contains spoilers for the film Pressure.

Meteorologists are rarely the heroes of major Hollywood movies. Never say never.

The new film Pressure is a lightly fictionalized version of the actual lead-up to the D-Day invasion of France by Allied troops during World War II, and the crucial role of meteorologists in deciding when that battle would happen. And it stars some big names.

Andrew Scott, most recently of Ripley fame, plays James Stagg, a Scottish meteorologist who is tasked with pulling together a D-Day weather forecast for Gen. Dwight D. Eisenhower, played by Oscar-winner Brendan Fraser.

Stagg is stressed out, to say the least. The movie’s title alludes both to barometric pressure, and to the enormous responsibility that the D-Day planners felt, given that so many soldiers were sure to die in the assault on Normandy’s beaches. The Allied commanders also knew that, if the invasion failed, the Germans would have the upper hand.

There was a lot of pressure on meteorologists to get the forecast right, says James Taylor, the principal curator at the Imperial War Museums in the United Kingdom. “They had an absolutely key role to play in the planning of D-Day.”

But the main drama in the film comes not from the interpersonal conflict between stressed-out weathermen in well-tailored uniforms, but from the science of weather forecasting itself. The movie depicts how a now-obsolete method of weather forecasting that was popular in the United States leading up to World War II was replaced by more modern methods that were taking root in Europe at the time.

“It’s really a seminal moment for the entire meteorological community,” says Louis Uccellini, who led the National Weather Service from 2014 to 2022. “And that was brought forward for societal benefit post-World War II.”

Here are three things that Pressure gets right about modern weather forecasts, according to scientists and historians.

WWII Weather Tip #1: The future doesn’t necessarily look like the past

Until World War II, weather forecasting in the U.S. mostly relied on a simple principle: past weather patterns are similar to future ones. Basically, look to the past to predict the future.

In the movie Pressure, that school of thinking is embodied by the meteorologist Irving Krick, who led the American forecasting effort for the Allies. In the days leading up to D-Day, “Krick was doing trend analysis,” explains Frank Blazich, a military historian at the Smithsonian’s National Museum of American History in Washington, D.C.

The D-Day invasion was originally planned for early in the morning on June 5th, 1944. “Eisenhower needed a really strong weather forecast,” Blazich says. “You need clear weather and a full moon to bring in aircraft at night,” as well as clear skies and no low clouds, so ships could see targets on shore clearly.

Krick was looking back at weather patterns that had occurred on that date in the past, to predict what would happen in 1944. And, based on the past weather, he was certain there would not be a storm. “Mark my words, D-Day will be calm and sunny,” Krick says in the film.

But other meteorologists disagreed. There were two other groups feeding weather information to Eisenhower, both of them staffed by European scientists. Their forecasts were based not on past patterns, but on real-time measurements of what was happening in the atmosphere from Newfoundland to Ireland. Those measurements clearly showed a storm headed for England and France.

In the end, the Europeans were correct, and D-Day was postponed to June 6.

After World War II, that new weather forecasting method took hold in the U.S., says Uccellini, and allowed for much earlier and more accurate weather forecasts, especially for severe weather events like hurricanes and other large storms.

“This is a basis for what we then saw in the rest of the century, in terms of being able to make predictions two, three, four, five, six days in advance,” Uccellini says.

Today, past patterns are even less useful for predicting the weather, as climate change alters global weather patterns and drives record-breaking storms and heat waves.

WWII Weather Tip #2: You can’t just focus on what’s happening at ground-level

In the days leading up to the D-Day invasion, the Allies had access to a lot of real-time information about conditions in the upper atmosphere, says Taylor of the Imperial War Museums. Without that information, they could not have predicted either the storm that delayed the D-Day invasion, or the lull in stormy conditions, which allowed the Allies to launch a surprise attack on the Germans just one day later, he explains.

Many of those measurements came from balloons. In the movie, which is directed by Anthony Maras, viewers are treated to lingering, moody shots of technicians wrestling with white weather balloons in windy weather, and of balloons traveling up through storm clouds over the Atlantic. The suspense builds as we and the film’s protagonists wait to learn what information the balloons sent back to the surface.

Today, such balloon measurements are still a crucial pillar of weather forecasts. The National Weather Service sends up hundreds of balloons every day, to monitor conditions in the atmosphere and keep track of how weather patterns are changing.

Radar, another technology that took hold as a result of World War II, is also a key modern forecasting tool that traces its roots back to World War II. The British used radar to spot incoming German bombers, but they were frustrated that the radar could also see rain. “For them, it was interference, in terms of being able to identify the aircraft,” explains Uccellini.

Many British radar scientists spent much of the war in the United States, where it was safer, and worked closely with American scientists, he says. “As soon as the war ended, the radar became a big topic within the meteorological community because of its ability to detect rainfall.”

The focus on what’s happening in the upper atmosphere has only deepened in recent decades. Since the 1980s, satellites have added another layer of granularity to our understanding of what is happening in the Earth’s atmosphere, often taking thousands of measurements every day.

WWII Weather Tip #3: More advanced science = better weather forecasts

One of the big takeaways from the movie Pressure is that better science can literally win wars.

The film closes with a quote from Eisenhower, who allegedly told John F. Kennedy that the Allies won the war because, “We had better meteorologists than the Germans.”

It’s unclear if this is indeed an exact quote from Eisenhower, or an apocryphal anecdote. Taylor and Blazich, both historians, were not aware of any original documents or accounts that verify the quote. The Eisenhower Presidential Library did not respond to questions about the quote.

Nonetheless, the sentiment that the quote expresses is valid, says Taylor. State-of-the-art weather science was a crucial piece of the puzzle when it came to planning D-Day and winning World War II.

More broadly, the film captures how investments in atmospheric science can lead to real-world applications that save lives, says Uccellini, and how outdated weather science can have devastating consequences.

That theme is particularly salient given the Trump administration’s efforts to cut staff and delay funding for climate science across every major federal science agency, including the National Science Foundation (NSF), National Oceanic and Atmospheric Administration (NOAA), NASA and university-affiliated laboratories that focus on atmospheric and climate research.

Staff cuts, retirements and a hiring freeze led to severe understaffing at the National Weather Service last year, although the agency has since hired hundreds of workers, following pressure from lawmakers and former weather service leaders including Uccellini.

The President’s budget proposal for next fiscal year asks Congress to make steep cuts to the NSF and other science agencies.

“I’m very concerned,” says Uccellini, “when I see cuts to the NSF, cuts to NOAA labs.” As climate change makes weather more dangerous, and less predictable, weather science becomes even more important, he says. In particular, he points to federally funded scientists working to understand how changes in the atmosphere affect things like flash droughts and extreme rainfall.