Alok Jha investigates how weather forecasting was transformed from superstition into science. At the heart of story is pioneering meteorologist, Robert Fitzroy. Driven to prevent disasters at sea - like the wrecking of a passenger ship off the Anglesey coast in 1859 - Fitzroy issued Britain's first storm warnings and came up with the first weather forecast to be published in a newspaper. Alok explores the knowledge Fitzroy was building on. He investigates weather folklore, asking if sayings such as 'red sky at night, shepherd's delight' have any merit. He tells the stories of the other heroes of meteorology - people like Evangelista Torricelli, a student of Galileo's, who invented the barometer; Luke Howard, who classified the clouds; and Francis Beaufort, who came up with the famous wind scale. Alok also discovers that public complaints about weather forecasts date back to the very first forecasts.

Alok Jha investigates how modern weather forecasting was born amid the horrific catastrophes of the 20th century, as meteorologists helped fight two world wars and tried to predict natural disasters across the globe. He tells the story of Lewis Fry Richardson, a visionary scientist who laid the foundations of modern computer-based weather forecasting in between shifts as an ambulance driver in the trenches of World War One. In Norway, Alok sees how meteorologists managed to unravel the mysteries of weather fronts and in India he sees how famines, which cost millions of lives, spurred meteorologists to try to understand climate on a global scale. Alok investigates how, during World War Two, weather forecasters, working from a secret camp outside London under the most testing wartime conditions, were called on to make the most important weather forecast in history - they were asked to predict if conditions would be good enough for the D-Day invasion to proceed. He sees how a family operating a tiny weather station on the west coast of Ireland became a key part of this extraordinary drama, as they provided weather readings that were vital to the outcome of the war.

The final episode tells the story of how meteorology became one of the most important scientific endeavours of the modern age. Alok Jha charts the progress of computer-based forecasting - the bedrock for how we do things today - through the characters who pioneered it. There's the American mathematician Jule Charney, who found a way to simplify weather for the early computers of the 1940s by listening to Beethoven, and the ambitious technocrat John Mason, who gambled the future of the Met Office on unproven technology in the early 1960s. Alok relives the moments that shook faith in forecasting to its core. He investigates the discovery of chaos theory, which threatened to undo all confidence in 20th-century science, and discovers the scientific consequences of that most infamous of all television forecasts - Michael Fish's missed hurricane, the Great Storm of 1987. Alok uses stunning science demonstrations to investigate the chaotic, unpredictable nature of weather. He meets present-day giants of meteorology like Tim Palmer and Julia Slingo, and observes one of the most powerful supercomputers in the world in action. Based in the Met Office HQ in Exeter, it's capable of simulating our entire planet's climate. It's a vital asset - one of the key tools that will help humanity face the vagaries of our weather and climate for generations to come.