A couple of weeks ago, more precisely on January 10, iridescent clouds were clearly visible all day long north of the Alps. I have never sighted any such occurrence and had no idea about this phenomenon. After taking a few photos I couldn’t resist researching the mysterious “rainbow clouds” on the web.
I was not able to find any easy explanation but from what I understand the strong foehn was causing the cloud iridescent. Here is another blog post and video, and here is a link to a German forum where people were posting pics.
Another effect of the foehn is a very clear air which allows us to get a clear view across the landscape for up to 300km (185mi) whereas under common weather circumstances the limit is around 50km (31mi). Above is a great example; the alps are around 150km south of Linz.
Check out my Linz Photo Stream for more pics!