Basque Country
 

Any ideas if I want to bike through Basque country? When would be the best season, sites to visit, worst case scenario?

Worst case?
 

I suggest you elaborate a little and say clearly what ever it is that is on your mind.

"Basque country" extends across both Spain and France, as does (for example) Catalunya on the other coast.

I've ridden through 'Basque Country' a few times, it's no different from the rest of Spain as far as being a tourist on a bike.

Pamplona is well worth a visit.