So the rain in Spain doesn't stay mainly in the plain?
There are places in Spain where it rains more than in the north, but only in a very small period of the year.
Last time I looked, Cádiz (in the very south of the peninsula) is the province with more yearly rain, also one of the sunniest. That's because it's in the straigth between Mediterranean Sea and the Atlantic Ocean. The (not very high, just about 1km height) mountains capture a lot of humidity.
And no, it's not a matter of "a small period of the year", but of a small portion of the province: Sierra of Grazalema.
Well, Spain is not entirely sunny. Certainly the north of Spain is not. You can see a darker line in the map that divides Spain. This is divided by a set of mountains called "Cordillera cantábrica" that makes the north way more rainy than the rest of Spain.
There are places in Spain where it rains more than in the north, but only in a very small period of the year. Most of the year is sunny there(the part that is not the north).