In reply to Belier:
We had the Cordillera Cantabrica one when we went in 1999. Is the same one?! The cover looks the same. Anyway, it did its job and was 100% better than the very old West Col(?) or Cicerone(?) one that we had previously. I've posted this before but it's worth another look. It's part of the introduction from that guide:
Proximity to the ocean and the humid climate of the Costa Verde ensure that the Picos are veiled by damp weather for much of the year. The immediate hinterland to the S is notably drier. In spring and early summer rainfall tends to be plentiful; cloud cover is frequent except during the evening. A fine off-shore rain from the Atlantic is known locally as orbayu. July and August have a combined average rainfall of 2 in. In this period dense mist attends early morning, followed, after short clear periods, by a cloud blanket until early evening. There might be days without rain when a luminous fog smothers the shining white limestone wilderness and defeats all the skill an experienced party can muster to find the way. The best continuous clear spell is recorded as the last week of August and the first two of September - often prolonged well into this month. Then an immense sea of clouds fills the encroaching valleys to a height of 1500m, while the summit areas stand out clear above it all day long. Violent winds can be experienced in all weather conditions between May and September. At other times the region is very wet with considerable snowfall...
Fabulous eh?