If you are looking for the "coolest" Costa in Spain in terms of temperature and climate, the Costa Verde (Green Coast) in Asturias and Cantabria is the top choice. Unlike the scorching Mediterranean coasts like the Costa del Sol, the Costa Verde stays significantly cooler due to its location on the Atlantic (Bay of Biscay). Even in the peak of summer, average highs rarely exceed 24°C (75°F), making it a refuge for those who find the southern Spanish heat unbearable. If you are looking for the "coolest" vibe rather than temperature, the Costa Brava in Catalonia is often cited for its artistic heritage (Dali) and rugged, high-end "boutique" atmosphere. However, for sheer physical cooling, the northern Atlantic coast remains the winner. The lush, rainy landscape earns its "Green" name, offering a mist-covered, temperate experience that feels more like the Scottish Highlands than the typical arid Spanish seaside, providing a perfect environment for hiking and exploring historic cider-making villages.