It may be joined at its shoulder to Europe, but meteorologically speaking, Spain has little to do with the rest of the continent. The Iberian Peninsula goes its own way weatherwise, generating its own pools of cold air in winter and dry-roasting on its own in summer. Even if it were as pancake-flat as The Netherlands, Spain would probably have interesting weather, situated as it is between the Atlantic – whose perpetually cool currents run south along the coast of Portugal – and the Mediterranean, which warms and cools with the seasons. Throw in a crisscrossing array of mountain ranges and a central plateau, and you have the makings of Europe's most diverse climate, one that would take a book to describe adequately. Entire seasons can be spanned by crossing from one mountain valley to the next, much less traversing the country.
As in most of Europe, winter brings a fair number of wet days across Spain, particularly along the lush north coast, where heavy winter rains have carved fjord-like inlets along the Catabrica peaks. Light snow falls on only a handful of days each year across the lower southern plateau, including Madrid. The snow is slightly more frequent across the northern plateau and far heavier and more persistent across the mountain ranges. The plateau also gets crisp, windy spells that may feel incongruously chilly to a visitor beneath the bright Spanish sun. The worst cold stays clear of the coastlines, which seldom drop to near freezing. The tables are turned in summer: coastal highs tend to average below 30°C/86°F while the interior heats up, especially across the lower elevations of the south.
Unlike the rest of the continent, Spain gets its most widespread moisture in the spring and autumn, as the polar jet stream migrates north and south, respectively. Especially in the spring, the rains tend to be showery, with thunder common in mid-summer, and there's typically plenty of sunshine before and after a warm-season storm. As the rains intensify again in September and October, the eastern Pyrenees and northern Mediterranean provinces fall prey to heavy downpours that can trigger dangerous flash floods with little or no warning. “Normal” is a slippery term for rainfall in this region, which is frequently either inundated or drought-stricken.
As you travel south along the coast, the climate becomes more classically Mediterranean. The Costa Blanca and, especially, the aptly named Costa del Sol bask in sunshine. Winters are mild and summers are warm, but seldom hot, with only moderate humidity. The rains from autumn through spring are little more than a brief distraction once a week or so, and when it's not raining, it's often crystal clear. The same applies throughout much of Andalucia, where there's little or no cloud on 100 to 150 days a year.
That much sun is bound to result in some heat, of course. The lowlands of Andalucia often soar above 38°C/100°F – sometimes a good deal hotter – in July and August. The air can be humid as well, albeit rain-free. Escape from the heat is close at hand, however. The Sierra Nevada carry snow year round, and the higher Pyrenees (including Andorra) tend to stay pleasantly cool as well. The Atlantic-cooled summer air on Spain's north coast is similar to that in Britain.