Hi Jean
Green Spain is lovely. Beautiful beaches and mountains and not very commercialised. We found the climate warm and pleasant in Spring and Summer but we, also, had some heavy rain.
We went one summer a few years back but drove down through France. Alan Rogers Europe guide has quite a few sites in Northern Spain and I imagine that there are even more in the Alan Spain/Portugal guide. The CC's Caravan Europe Vol is, also, very helpful. We got all of our sites from these 2 books (cheapest on Amaazon UK)
We, had visited the area on a fly-drive package in the preceeding spring before taking the caravan in the summer and had hoped to tour right along the northern coast in the summer. Unfortunately our car suffered a major breakdown which meant that we were restricted to a small site where we were taken by breakdown truck, very primitive, and Camping Playa Joyel where we were later towed to by breakdown truck.
Camping Playa Joyel at Noja which is quite a sophisticated site used by UK operators. It is only about 70km the ferry port at Santander.
We visited a few sites for a look in the spring with a view to returning in the summer. If I remember correctly Camping Hortensias at La Franca was very close to the beach and one we liked the look of that Camping La Paz at Llanes was, also, an interesting site on a steep headland with lovely views.
I would recommend the scenic drive from Potes to Fuente de where there is a cable car up into the Picos de Europe mountains. There are a couple of pleasant sites near to Potes which is a pretty riverside town.
We have meant to return but there are SO MANY lovely places to visit.
I'm sure you'll have a super time.
Tim