I should have known when I got up this morning.

This morning when I got up, even the tom-cat was ill and to prove it he ran into the bathroom twice, after I had cleaned up, to throw up on the bathroom floor again.
I admit that I was thankful for him using the lino in the bathroom and not the carpet in the living room (wonder where he learned that?) but I wasn't feeling too well myself.
In fact, I felt as if I had spent the night drinking, whereas I had, in fact, been a very good boy, drank only mineral water and went to bed early (by my standards anyway).

It was cold and windy when I opened the door to go to work. Then it started to rain while I was on the motorway. My headache got worse during the morning so, to be able to concentrate, I was forced to take a couple of paracetamol.

When I went for a sandwich at lunch time the sun was shining brightly, there were wispy clouds in the sky and the temperature had risen by at least 10°. The mountains looked, as if they were about to fall on top of me!
I should have known - Föhn!

When I lived in Stuttgart, I regularly heard my friends in Munich complaining about the Föhn - I always laughed, I'd never heard such rubbish! When I started training people in Switzerland I had trouble with one of my very first courses, due to a very bad headache. 'Of course,' my colleague said 'there is a Föhn'.

And he was right - I have the symptoms nearly every time.

Wikipedia tells us, that a foehn wind occurs when a deep layer of prevailing wind is forced over a mountain range (Orographic lifting). As the wind moves upslope, it expands and cools, causing water vapor to precipitate out. This dehydrated air then passes over the crest and begins to move downslope. As the wind descends to lower levels on the leeward side of the mountains, the air heats as it comes under greater atmospheric pressure creating strong, gusty, warm and dry winds. Föhn winds can raise temperatures as much as 30°C (54°F) in just a matter of hours. Winds of this type are called "snow-eaters" for their ability to make snow melt rapidly. This ability is based not only on high temperature, but also the low relative humidity of the air mass. Föhn winds are also associated with the rapid spread of wildfires, making some regions which experience these winds particularly fire-prone.

Whole villages along the northern foot of the mountains have been burned down during a Föhn. One village, I remember reading (I can't find the link) burned to the ground more than once.
As recently as February 2001, a fire that started in the centre of Balzers (just round the corner here, in Liechtenstein), burned down half the old town centre. This, even though the local fire brigade was out practising and reached the source of the fire within minutes.
They immediately alarmed the fire brigades of the two neighbouring towns but even so, a total of 9 Houses and 6 barns were destroyed completely and 3 houses were badly damaged.

After taking those facts into consideration, I suppose my headache is almost nothing!
I shall never laugh at anyone who complains about the Föhn again.