There are vast differences between north and southern Spain, so much so that we find it easier to think of Spain as a 'united nations' of distinct regions. The size and location of the country creates huge variety in terms of climate, topography, culture and cuisines. Here's a quick summary:
Climate
A big difference is the climate. Southern Spain is characterized by long, dry and sometimes very hot summers. The north is much cooler and has more rainfall, thereby keeping the landscapes lush and green. So whereas you wouldn't want to visit Andalucía in the south in the height of summer, July and August are some of the best times to visit northern Spain. Conversely, the winters can be a bit wet and wild in the north, whilst in the south it's much drier and more mild, generally speaking.
Landscapes
Because of the higher rain and plenty of sunshine, the dominant color of the landscapes in the north is green. The coastal pastures are positively vibrant; grapes ripen in the verdant vineyards of Rioja and Europe's second-biggest beech and fir forest spreads along the slopes of Navarre in the foothills of the Pyrenees.
Some of Spain's best beaches dot the coast too. The northern coast has much more in common with the Atlantic coast down in the south than the Costa del Sol. Both up here in the north and along the Costa de la Luz in the south, the beaches tend to be found alongside small fishing towns or in coves which interrupt rolling cliffs. This is not a place of resorts. The coastline has a wild feel in places, not least around Zumaia in the Basque Country, where you'll find the flysch coast. Deriving from the German word for 'glide', thin vertical sheets of rock create spectacular rocky stripes down the cliffs and into the Cantabrian sea. It's stunning to look at and you can either walk around the headland if the tide is out, or follow the original Camino route along the clifftops.
Inland from the coast, the dramatic mountains of the Picos de Europa rear up in spectacular style. What makes them different to the peaks of the south, aside from their sheer scale and beauty, is their proximity to the sea. You can stand with your toes in the sand on the beach in Asturias and look up at the summits, sometimes capped with a dusting of snow.
Culture
The culture and ways of life are very different too. Modern Spain can trace much of its cultural fabric back to the 8th century when the Moors crossed the Strait of Gibraltar from north Africa into southern Spain. From there they spread across the Iberian Peninsula, influencing the cuisine, architecture and lifestyles of Spain, all the way from Andalucía up as far north as the Picos de Europ and Pyrenees mountains. However, they never quite conquered northern Spain. Meeting resistance in the Picos de Europa, the Castilians began to push the frontier between Islam and Christianity south again. This is why the original Camino de Santiago pilgrimage route ran along the north coast before the inland route became more popular once the Castilians gained control again.
So what does this mean for you and your travels? Whereas Andalucía is awash with the glories of the Islamic age, from the famous Alhambra Palace and Mezquita mosque to the white villages and a diet which includes dates, apricots and oriental spices, the north has a very different feel. There is little in the way of Moorish heritage here and the culture feels much more related to northern Europe. But there is a lot to love about the north...
One of the joys of traveling in northern Spain is that the regions all feel distinct. The Basque Country in particular is proudly different and very independent; its customs, cuisine and language are all very much its own. Winemaking heritage runs deep in Rioja, as does the tradition of pilgrimage on the routes to Santiago. From the traditional fishing harbors and the shipwrecks of Galicia's Costa de Morte, you'll see that the northern regions retain a strong connection to the sea through their industries, traditions and storytelling. But cultural links stretch back much further into times, as you'll see in the plethora of ancient monuments and primitive cave art.
Food & drink
Finally, the food on your plate and the tipple in your glass are different too. The south of Spain is the world's greatest producer of olive oil, in both quality and quantity. This, along with a thriving wine industry, is a legacy of the Greeks and Romans who first brought olive trees and vines to Spanish shores.
When we think of Basque food, for example, the fruits of the sea come more easily to mind, particularly salt cod. One thing that unites north and south is the idea of tapas, known as pintxos in the north. The name comes from the verb 'pinchar', which means 'to pierce' and refers to the skewers which hold the little culinary works of art together. Pintxos are a huge deal in the Basque Country and Navarre and the bars of Bilbao, San Sebastián and Pamplona compete between themselves to create the best offerings. It's a part of the culture we love to share in the company of a local expert.
North of Rioja, the vineyards peter out and are replaced by apple orchards. Asturias, Navarre and the Basque Country are Spain's greatest producers of cider and are all fiercely competitive when it comes to who makes the best.
A tradition of cheesemaking unites the northern regions. The traditional shepherd economy based on sheep and goats herded in the high pastures has evolved to an easier farming life based on cattle and cheesemaking facilities in the valleys, but you can still enjoy glimpses of traditional farming and enjoy great quality cheese, from the Basque Country across to Asturias.