A heatwave swept across Europe in 2003, making it the hottest summer since 1540. With forecasters noticing similar weather patterns in Switzerland this summer, could this August be as hot as the one 22 years ago?
Current forecasts show that temperatures will vary from 16C to 30C across Switzerland at the start of August, well below 2003 levels.
On 11th August 2003, temperatures reached 41.5C in Grono, in the canton of Graubünden, the highest temperature ever officially recorded in Switzerland.
And now meteorologists have spotted similarities between the weather patterns in two summers, making a similarly roasting August a possibility.
The June months of 2003 and 2005 were both marked by frequent high-pressure systems, which meant “an extraordinary amount of sunshine and high temperatures,” meteorologist Michael Eichmann wrote on the blog of Swiss weather service MeteoNews.
June 2003 in Switzerland was the hottest since measurements began in 1864 and June 2025 came a close second, Eichmann said, noting that the regional pattern of average pressure distributions was similar in both years.
Such parallels allow “initial, cautious conclusions to be drawn for August,” he said.
Using Zurich as an example, Eichmann noted similarities in the summers of 2003 and so far in 2025.
“After a very warm to hot June, there was quite a temperature setback at the turn of the month in 2003, which also followed – with a slight delay – this year. After that, there were a few hot days again until the end of the month, but the situation only stabilised again in August,” he wrote.
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In 2003, a stationary high-pressure system built up over Europe with high pressure over the UK blocking Atlantic currents – which typically bring cooler weather. The currents therefore had to move northwards and so didn’t reach Switzerland.
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This meant that August was by far the hottest since records began, with temperatures 3.5C higher than the long-term average.
There’s a chance that August 2025 could see similarly hot temperatures as models are again forecasting high-pressure weather for the UK, the meteorologist added.
If this proves to be the case, then the currents could again be deflected to the north, although Eichmann cautioned that it was impossible to accurately predict the weather so far in advance.
“With weather forecasts, small model deviations can ultimately lead to large differences between the model and reality, and each year is unique and writes its own chapter. At the end of August, we will draw a definitive summer balance,” he wrote.
