Sea temperature in Spain month by month
Water lags behind air: in June it's hot but the sea is still cool, and in September the reverse. Here are the figures by coast.
Why the sea lags
Water takes far longer than air to warm and to cool. That's why the hottest month of the year isn't the month with the warmest water: the sea accumulates a whole summer's heat and peaks in August and especially early September. It's why the first half of September is the best swimming window of the year.
Mediterranean
Around 14 or 15 degrees in February, rising to about 18 or 19 in May, reaching 24 or 25 in July and around 26 in August, and holding above 25 through the first half of September. In October it drops to about 22, still perfectly swimmable for many people.
Cantabrian coast
Considerably colder all year: 12 to 13 degrees in winter and around 20 or 21 at the height of summer. That's genuinely cold water for anyone used to the Mediterranean, and long swims aren't comfortable unless you're accustomed to it.
Southern Atlantic: Cádiz and Huelva
A middle point. Around 16 degrees in winter and 21 to 23 in high summer. Slightly cooler than the Mediterranean, with the advantage of much wider, less crowded beaches.
The Canaries
The big difference: 19 to 20 degrees in the coldest months and 23 or 24 in the warmest. That makes the archipelago the only part of Spain where swimming is comfortable twelve months a year.
When the season starts and ends
In the Mediterranean, for most people the comfortable season runs June to October. On the Cantabrian coast, July and August and little more. In the Canaries, all year.
The detail that saves money
If the goal is swimming, June and the first half of September have perfectly good water at prices well below August. Shifting your dates by two weeks can mean half the accommodation cost with the same sea.
Allow for variation
These figures are rough averages. There's variation between years, between areas of the same coastline, and occasional cold-water episodes caused by currents. Check the specific forecast for your beach before relying on an exact figure.
Keep reading
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