Image copyright MeteoSwiss Image caption The Eiger is crisp and clear on the days when the Foehn blows

It's common to hear people say that weather affects their health. Many, for example, claim that joint pain, the increased twinge of an arthritic knee perhaps, is a sure sign that cold wet weather is on the way. But how much do weather phenomena, or changes in the weather, really affect our health? That's a question BBC World Service programme Crowd Science is investigating this week.

For centuries, people in the Alps have attributed health issues, headaches in particular, to the mountain wind known as the Foehn. It is, alpine communities insist, a very special wind, with very special properties.

"It is a very strong wind," explains Ludwig Z'graggen of Switzerland's Federal Office of Meteorology (MeteoSwiss). "It can blow at speeds of 150km/h, and it is also a very warm wind. In the middle of winter, we can see temperatures of 20 degrees centigrade in the Foehn valleys."

That warm dry wind roaring down from the mountain glaciers occurs when moist air builds up on the southern side of the Alps.

"As soon as it reaches the (alpine) divide the air descends, and while descending, the air warms," explains Peter Stucki, a climate historian and Foehn specialist at Berne University. "It gets drier and speeds up; we call it a down-slope wind storm, or a lee warm-air flow."

But is this really something special? "It's our Swiss cheese," continues Mr Stucki. "Others - they have hurricanes, they have cyclones. We have the Foehn."

Image copyright MeteoSwiss Image caption Do modern weather forecasts somehow play a role in making people think they will get a headache?

And a key reason the "snow eater", as this warm alpine wind is sometimes called, is viewed as special is the effect many claim it has on their mood, and their health.

The issue was recently the subject of an hour-long programme on Swiss radio, during which listeners phoned in to swap symptoms.

One woman described feeling low, and having a headache when the Foehn was building up, but then being full of energy when it finally started blowing.

A man said he believed the wind was a challenge, in a positive way, because it "shakes us up a bit".

Swiss pharmacists are used to customers seeking help because of alleged Foehn-related symptoms.

"It can really be a problem, the Foehn headache," says Berne pharmacist Daniel Wechsler. "I think there is a relation between weather and health problems, yes."

Mr Wechsler and his staff can prepare special plant-based remedies to help, although he confesses most people request conventional medicines, such as aspirin or "something that acts fast".

And what about Mr Wechsler, himself? Does he feel the effects of the Foehn? "No, not at all, no. Every weather is fine for me."

'No link'

Dr Andreas Gantenbein, a neurologist and president of the Swiss Headache Association, agrees that many patients complain about the effects of the Foehn, and, he says, their symptoms and concerns must be taken seriously.

But, he told Swiss radio, there was no real scientific evidence linking the Foehn, or other winds, and headaches.

A study into the North American wind called the Chinook suggested a possible link, but the study was too small to be conclusive, while larger studies in Germany and Austria into the Foehn itself showed no link.

And Ludwig Z'graggen of MeteoSwiss suggests that the historic belief that the Foehn causes headaches, combined with modern weather forecasts which warn that it is on the way, may also be a factor.

"People get headaches when they hear the Foehn is coming," he says.

"Even among scientists we are not all of the same opinion," adds Peter Stucki on Berne University. "One (of my colleagues) said that's all nonsense; another said 'no, I am quite sure I can feel the Foehn'."

"My personal feeling is you might be more sensitive to variability in (barometric) pressure when you are more stressed."

Image copyright MeteoSwiss Image caption Moist Mediterranean air blows over the Alps and then descends, warming as it drops into valleys

What is clear is that the Foehn is regarded not just as special, but with great affection by people in the Alps, despite the negative effects some claim it can have.

When that dry warm wind blows, it sucks all the moisture out of the air, meaning the visibility is uncannily clear. On a Foehn day, the Eiger, a good 60km from the Swiss capital, Berne, looks close enough to touch.

"You have an incredible view, you can see for miles and miles and miles," says Berne resident Katja Maeder Zuercher.

"In our over controlled world the Foehn is something still untameable," suggests Peter Stucki. "And we like that. It's something we actually love. We love the wildness; we love the natural force of the wind."

And Ludwig Z'graggen admits he even makes a special trip to one of the Foehn valleys when his beloved wind is blowing. "I like this strong wind, this warm wind, the singing of the trees and the clear air... I love the Foehn. I can’t live without the Foehn."