Historical Weather Info ?
 

I'm researching weather trends at European airports and I'm trying to find historical METARs (observations going back for a few years). Does anyone know of an on-line source for this type of info ?

You can get more generalised Climatological data for individual UK airports from thr Met Office Web site now, such as percentage of foggy, snowy, low cloud days, and then compare airport to airport. But I dont think old METARs themseleves available.

In the UK the records exist - and I suspect this is the same the world over. Here the Met Office keeps it for climatological monitoring purposes etc.

The trouble is that they will probably charge you for access to it. A strange concept really when you consider that the information is often not even originated by Met Office staff but by airport staff (although it's true that the Met Office were far more involved in years gone by)!

More practically, you'll often find that the airports keep the information locally and they might be prepared to let you see it if you explain it's not for commercial use. Having said that, it would be no small task to extract trends from some of the records - until recently these were commonly kept on paper in handwritten form.