Spain is a large country and therefore the weather can vary greatly depending on which region you head for and when.
As a general guide, unless your plan is to do nothing other than lie basted in suntan oils for extended periods of time and drinking cold beer on Spain’s beaches, the best times to visit are Spring and Autumn when not only are the temperatures more manageable but you will have to share space with substantially less tourists. Let’s face it, even though we are tourists ourselves, it doesn’t necessarily mean that we want to hang out with other people doing the same. Spain puts up with well over thirty million tourists every year and most of those thirty million arrive during June, July, August and September.
August is a very bad time to visit Spain’s coasts as this is the hottest month of the year and also the month when Spaniards themselves head for the beaches. Cities during August are often quiet and many shops will close down for part of or in most cases the entire month.
The south is warm almost the entire year and is an ideal location during the winter if you are hunting for some winter sun to warm your chilly bones. Whereas in the extreme north, the climate can be very cold and windy and comparable to parts of England, Ireland, Holland and Germany.
If you are into hiking, then again spring and autumn are the best times to visit. September and October can still experience what would be considered hot days in other countries, so starting hikes out early in the day is still a good idea – depending where in the country you are.