Britain braces for deep depression: storms spoil tea. Storm Ciaran cut an invisible path of chaos across southern Britain last autumn, ruining 20 million people’s chance of getting a cup of tea for breakfast, new research suggests.

Meteorologists at the University of Reading found that record low pressure during the storm meant that the boiling point of water was below the critical 100 degrees Celsius needed for good coffee. In a study published in the journal WeatherScientists reported that water in Reading boils at just 98°C.

During the storm on the morning of Nov. 2, Caleb Miller, Ph.D., a student and co-author of the study, quickly set up equipment in the Meteorology Department labs to accurately measure the boiling point of water.

“Storm Ciaran highlighted the wind and rain that was lashing the UK from the outside,” Miller said. “As an experimentalist, I took the opportunity to make some measurements of the properties of boiling water at low atmospheric pressure.” Co-author Dr Alec Bennett said: “The effect of pressure on boiling point has long been known to mountain climbers, but Ciaran extended this effect to a wider area.”

Under pressure

The researchers conducted controlled experiments using sensitive temperature sensors and a standard electric kettle. They compared the results with previous boiling points observed under different air pressure conditions using the same device. Together, these experiments showed a clear relationship between air pressure and boiling point.

To investigate the storm’s broader regional impact on boiling points, the researchers combined weather data from multiple sources, including pressure readings from the University of Reading’s Atmospheric Observatory and data from roadside weather stations in southern England. This helped them track how the storm moved across the region during breakfast. They found that low pressure moved northeast across the region early in the morning, in time for typical breakfast time.

At the height of Storm Ciaran’s impact, the boiling point of water in some areas dropped to just above 98°C, around 2°C below normal conditions. Tea experts consider the ideal brewing temperature to be between 98°C and 100°C. Water below this range will not extract the full flavour from the tea leaves.

Lead author of the paper, Professor Giles Harrison, said: “Like many Brits, I need my morning tea. While I knew that the boiling point of water varies with atmospheric pressure, I didn’t expect the storm to eliminate the boiling point. Water temperatures outside the recommended range for making good tea may have little effect.”

The study estimates that around 20 million people in London and south-east England were potentially affected by this phenomenon, which could theoretically have made tea less palatable for a large portion of the UK population that morning.